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A POPULAR 




Handbook and Atlas of Astronomy. 



A POPULAR 



Handbook and Atlas of Astronomy. 



AS A COMPLETE GUIDE TO 

.^ ^noluleiigc of the ^cabenb ^oiics: anb as an ,^ib 
to those ^jossessing ^clcsto^jes. 



BY 

S/ WILLIAM PECK, F.R.S.E., F.R.A.S., 

ASTRONOMER TO THE CITY OF EDINBURGH, LECTURER ON ASTRONOMY, 
AUTHOR OF " THE CONSTELLATIONS AND HOW TO FIND THEM," ETC. 



CONTAINING 



FORTY-FOUn LARGE PLATES, A^^D NUMEROUS ILLUSTRATIONS, 
DIAGRAMS, cC-c. 




G. P.- PUTNAM'S SONS, 27 & 2 9 WEST TWENTY-THIRD ST. 

LONDON: (;ali. and inglis. 



1S91. 






B».*ter^SS)l>C' I.»«J« ' 




0) 



:j^M.im.MM-(M'M. 



In the production of this work the Author had in remembrance ^vhat he had one time seen so well stated 
— viz., "That the public now demand of those devoted to science, that they shall not confine the knowledge they 
have such favoured opportunities of acquiring, to the lecture-room, but shall render it, us far as practicable, available 
to the well-informed of all professions." While keeping this in view, however, he did not think it necessary that 
the present work should be of an elementary nature, nor, on the other hand, an advanced work, but one well 
suited to occupy an intermediate position, and to give the kind of information so often required, yet sometimes 
difficult to obtain from ordinary Avorks on the science. 

The various subjects, therefore, are described in a popular manner, while, at the same time, complete and 
accurate information is given in the principal departments of modern astronomy. More than this, however, is 
occasionally required, and so numerous important Tables, Avhich are too often omitted in works of a similar nature, 
have been inserted for ready reference on the part of the student. The object has been, in short, to supply 
the knowledge that is required by every fairly well educated individual — viz., to give a clear, accurate, and popular 
account of the nature of the various heavenly bodies, and their position in the universe. 

In the first chapter, in a condensed form, there is presented the Author's investigation as to the origin of 
the Constellations, which at some future time he hopes to fully elaborate in a special work. These ideas are 
now for the first time published, and are the outcome of many years' study of the subject, particularly from a 
source that, strangely enough, has not hitherto been much considered — the positions of the old constellation figures, 
and the testimony of the star-groups themselves. 

The principal subjects discussed in the various chapters are arranged under different heads, an arrangement 
which, it is hoped, will facilitate reference, and at the same time give a clearer idea of the more important points. 
It will be seen that the large plates — 45 in all — form a special feature of the volume. In most astronomical works 
a considerable amount of clearness is lost for Mant of sufficiently enlarged diagrams. The present M-ork, it is 
hoped, will be entirely free from this defect. The plates of views, charts, diagrams, &c., have been specially 
constructed by the Author himself, and no labour has been spared in making them as accurate and comprehensible 
as possible. 

The Atlas proper will be found of the greatest assistance to all ■who are desirous of obtaining, in the simplest 
manner possible, an accurate knowledge of the sidereal heavens. The charts being printed on a dark blue ground 
with white stars (which is decidedly preferable to the ordinary method of black stars on a ^vhite ground), the 
constellations are represented in a natural manner, and the identification of stars greatly facilitated. The twelve 
large charts, wliich embrace the whole star-sphere, combined with the twenty-four index horizon maps, whereby 



PREFACE. 



the position of the constellations in the sky can be ascertained from any part of the globe, and for any time of 
the year, form an Atlas which, we hope, will be one of the plainest and most complete for ordinary purposes 

hitherto published. 

Throughout the work the wants of the telescopist have not been lost sight of, especiaUy in the Atlas portion, 
which Willie found to contain the fuUest information about the various objects which may with advantage be 
examined by a small instrument. In short, it is believed that little has been omitted that would have in any way 
increased the attractiveness and usefulness of the volume, and that would increase its value as a suitable companion 
for all those desirous of possessing a knowledge of the heavenly bodies. 

Altogether, it is hoped that the volume may be the means of creating an interest, however slight, in the wonders 
that lie stored in the depths of infinite space. 

MURRAYFIELD MiD-LoTHIAN, 1890 




Contents 



-»*<- 



PAGE 
V 

vii 
ix 

X 

xi 



PREFACE, ... 

CONTENTS, ... 

LIST OP LARGE PLATES, 

LIST OF ILLUSTRATIONS IN THE TEXT, .. 

LIST OF TABLES OCCURRING THROUGHOUT THE WORK, 

CHAPTER 

I. THE CONSTELLATION FIGURES— THEIR PROBABLE ORIGIN— 

The oldest records of the Constellations ; The Sphere of Eudoxos ; The use of the Zodiac ; The country in 

which the Constellations were originated ; The epoch at which thej' were invented, ... ... ... 1 

II. MOVEMENTS OF THE EARTH WHICH AFFECT THE APPEARANCE OF THE HEAVENS— 
Diurnal Motion ; Annual Motion ; Precession of the Equinoxes ; Nutation ; Aberration ; Proper Motion ; 

Alterations in the appearance of the Constellations ; The actual velocity of Stars, ... ... ... 11 

III. THE SIDEREAL HEAVENS- 

The Stars ; their distances ; Parallax ; The Nature of the Stars ; Different orders of Stars ; Double and 
Binary Stars ; Variable and Temporary Stars ; Star Clusters and Nebulce ; The Number of the Stars ; 
The Milky Way, ... ... ... ... ... ... ... ... ... ... 19 

IV. THE SUN— 

Its distance from the earth according to the ancients ; Modern determinations of the Sun's mean distance ; 
Its Volume and Mass ; Sunlight and Heat ; Sunspots ; Faculae ; The Sun's Interior ; The Solar 
Atmosphere; Principal Facts about the Sun, ... ... ... ... ... ... ... 33 

V. THE PLANETARY SYSTEM AND ITS VARIOUS MEMBERS, 39 

The Planets nearest the Sun, ... ... ... ... ... ... ... ... 40 

Mercury ; Transits of Mercury, ... ... ... ... ... ... ... ... ... 41 

Venus ; Transits of Venus, ... ... ... ... ... ... ... ... ... 43 

The Earth ; Its movements ; The Year ; The Day ; Variation of the eccentricity of the terrestrial orbit ; 

The observed obliquity of the Ecliptic for nearly 3000 years, ... ... ... ... ... 45 

Mars; Its continents and oceans ; Its snow caps ; Its satellites ; Their size ; Their rapid movements, ... 48 

The Asteroids; Their position ; Their number, ... ... ... ... ... ... ... 51 

Jupiter; Its gigantic size and mass ; Its cloud zones ; Its atmospheric storms ; Its heat ; Its satellites, ... 53 
Saturn ; The wonderful ring system ; Its dimensions and nature ; The satellites ; A miniature of the Solar 

System, ... ... ... ... ... ... ... ... ... ... ... 55 

Uranus; Its Moons ; Their paths, ... ... ... ... ... ... ... ... 58 

Neptune; Its wonderful discovery ; The direction of its rotation, ... ... ... ... ... 59 

Trans-Neptunian Planet, ... ... ... ... ... ... ... ... ... 60 

Principal elements of the Planetary System for 1900, ... ... ... ... ... ... 61 

Principal elements of the Satellites, ... ... ... ... ... ... ... ■•■ 62 

Principal Facts about the Planets, ... ... ... ... ... ... ... ... ... 62 

VI. COMETS AND METEORS— 

Comets ; Their paths and movements ; Different classes of comets ; The heads of comets ; Their tails ; The 
principal comets belonging to the Solar System ; Meteors and Meteor Systems ; Occurrence of Mtteor 
Showers ; Meteorites ; Their size and composition ; The Origin of Comets and Meteors, ... ... 03 

vii 



viii CONTHNTS. 



CHAPTER 

VII. THE MOON— 



Table 


1. 


)> 


2. 


n 


3. 


>5 


4. 


1) 


5. 



PAGE 



The Lunar Phases ; The Month ; different kinds of month ; The Lunar Orbit ; Dimensions of the Lunar 
Globe ; The Eotation of the Moon ; Libration in latitude and longitude ; Telescopic appearance of the 
Luuar Globe ; Lunar Mountains and Craters ; Diameters of the more interesting craters and walled 
plains ; Lunar Elements, ... ... ... ... ... ... ... ... ... '^2 

VIII. ECLIPSES OF THE SUN AND MOON— 

The fear produced by eclipses in superstitious ages ; The Saros ; Eclipse Seasons ; Eclipses of the Moon ; 

Eclipses of the Sun ; Solar Eclipses till 1900 ; Lunar Eclipses till 1900, ... ... ... ... 82 

IX. ASTRONOMICAL INSTRUMENTS FROM THE EARLIEST TIMES— 

The instruments used by the ancients ; The Gnomon ; The Astrolabe ; The Parallactic Rules ; Tlie invention 
of the Telescope ; Refractors and Reflectors ; The Modern Reflector ; Application of the Telescope ; The 
Parallel Wire Micrometer ; The Transit Instrument ; The Observatory Clock ; The Equatorial ; The 
Spectroscope; The Altitude and Azimxith Instrument ; The Sextant, ... ... ... ... 90 

Suitable instrument for a practical study of the heavens, and method of using it, ... ... ... 108 

X. EXPLANATION OF THE STAR CHARTS— 

The Ancient and Modern Constellations ; Designation of individual Stars ; Magnitudes of Stars ; Number of 

Stars of each magnitude visible to the unaided eye ; Star Charts ; Explanation of Tables, &c., ... ... 112 

THE CONSTELLATIONS INSERTED IN THE STAR CHARTS, ... ... ... ... ' 118 

FOR FINDING THE APPARENT TIME OF SUNRISE AND SUNSET AT DIFFERENT 

LATITUDES FOR ANY TIME OF THE YEAR, ... ... ... ... ... 120 

THE EQUATION OF TIME, ... ... ... ... ... ... ... ... 121 

THE DURATION OF TWILIGHT AT DIFFERENT LATITUDES, ... ... ... ... 121 

FOR FINDING THE STARS VISIBLE AT ANY DATE AND HOUR IN THE NORTHERN 

HEMISPHERE, ... ... ... ... ... ... ... ... ... 122 

„ 5a.. FOR FINDING WHEN A STAR IS ON THE MERIDIAN, ... ... ... ... 123 

„ 6. FOR FINDING THE STARS VISIBLE AT ANY DATE AND HOUR IN THE SOUTHERN 

HEMISPHERE, ... ... ... ... ... ... ... ... ... 124 

„ 6a. FOR FINDING WHEN A STAR IS ON THE MERIDIAN, ... ... ... ... 125 

7. SIDEREAL TIME AT NOON FOR VARIOUS DATES, ... ... ... ... ... 126. 

„ 8. FOR FINDING THE TIME OF RISING OR SETTING OF A STAR, ... ... ... 126 

„ 9. STAR CATALOGUE GIVING THE NAMES, POSITIONS, AND MAGNITUDES OF THE MORE 

IMPORTANT STARS FOR EPOCH 1890, ... ... ... ... ... ... 127 

INDEX TO THE CHART OF THE MOON, ... ... ... ... ... ... ... ... 136 

CATALOGUE OF INTERESTING OBJECTS THAT MAY BE SEEN WITH A TELESCOPE, ... ... 150 

INDEX, ... ... ... ... ,., ... ... ... ... .., .. _^ 273 



LIST OF LARGE PLATES. 



«5*e- 

PAGE 

Frontispiece. Photographs of the Moon taken by the Author, ,.. ... ... ... ... Facing Title. 

Photographs of an Eclipse of the Moon taken by the Author, ... ... ... ... 86 

Plate 1. The Old Constellation Figures in the Northern Hemisphere, ... ... ... ... ... 2 

„ 2. Do. do. Southern Hemisphere, ... ... ... ... ... 2 

,, 3. The Positions of the Constellations in the Northern and Southern Hemispheres 14 700 years ago, ... 10 
,, 4. The Stars Visible to the Naked Eye in the Northern and Southern Hemispheres, ... ... ... 19 

„ 5. The Telescopic Appearances of the more interesting Double Stars, ... ... ... ... 24 

„ 6. Tlie Pleiades, from a Photograph, showing the Nebulte surrounding the Brighter Stars, ... ... 2G 

„ 7. Star Clusters, ... ... ... ... ... ... ... ... ... ... 28 

„ 8. Nebulae, ... ... ... ... ... ... ... ... ... .-■ 29 

,, 8a. The Spiral Nebula in Canes Venatici, ... ... ... ... ... ... ... 30 

„ 86. The Dumb-bell Nebula as seen by Lord Rosse, ) 
Nebulae as seen by Sir J. Herschel, ... j 

„ 9. The Sun, showing the Sun-spots, Faculse, Prominences, Corona, &c. (CoZoztrec^, 
,, 10. The Comparative Sizes of the Planets {Coloured), 
„ 11. The Orbits of the Inner Planets, ... 

„ 12. Chart of the Planet Mars in Two Hemispheres, from Eecent Observations by Schiaparelli (Coloured), ... 
„ 13. The Solar System ; with Orbits of Comets ; and Enlarged Chart of the Orbits of the Principal Asteroids, 
„ 14. The Orbits of the Satellites of the Planets, ... 
,, 15. Telescopic Views of the Planets (CoZowrec^), 
„ 16. Views of the More Remarkable Comets, 
,, 17. Lunar Craters, 

„ 18. Diagram of Solar and Lunar Eclipses, 
,, 19. Spectra of the Sun, Stars, Nebulee, &c. (Co^o?/re(i), ... 
„ 20. Chart of the World on the Stereographic Projection, showing the difference of time between different 
places ; the duration of the longest and shortest days at different latitudes ; and the positions of the 
principal Observatories of the world (Co^oJtrec/), ... ... ... ■■■ ... ... 116 

Picture Chart of the Moon, ... ... ... ... ... ... ... ... 136 



32 

36 
39 
42 
50 
5-2 
54 
56 
66 
78 
88 
106 



Star Charts. 

Circular Maps, Nos. 1 to 12, for Finding the Stars Visible at Different Dates and Hours in the Northern 

Hemisphere, ... ... ... ... ... ... 137-142 

„ ,, „ 13 to 24, for Finding the Stars Visible at Different Dates and Hours in the Southern 

Hemisphere, ... ... ... ... ... ... 143-148 

DECLINATION. EIGHT ASCENSION. 

Indicates from 50° N. to 90° N., and from h. to 24 h., ... ... ... ... ... 150 

152 
154 
156 
158 
160 
162 
164 
166 
168 
170 
172 
172 



Chart 1. 


)> 


2. 


55 


3. 


)) 


4. 


»» 


5. 


)> 


6. 


>» 


7. 


)) 


8. 


IJ 


9. 


J) 


10. 


'5 


11. 


)5 


12. 


n 


13. 



10° s. to 50° N., 




21 h. , 


, 3h., 


10° 8. to 50° N., 




2h. , 


, 8h., 


10° s. to 50° N., 




7h. , 


, 12 h., 


10° s. to 50° N., 




12 h. , 


, 17 h., 


10° s. to 50° N., 




16 h. , 


, 22 h.. 


10° N. to 50° s., 




Oh. , 


, 5 h., 


10° N. to 50° s., 




4h. , 


, 10 h.. 


10° N. to 50° s., 




9h. , 


, 15 h., 


10° N. to 50° s., 




14 h. , 


, 20 h., 


10° N. to 50° s.. 




19 h. , 


, Oh., 


50° s. to 90° s.. 




Oh. , 


, 24 h., 



The Zodiacal and E(juatorial Regions of the Star Sphere, 



LIST OF ILLUSTEATIONS 

Occurring in the Text. 



to the Precession of 



to Proper 



-**<- 

FIG. 

1. The Sphere of Eudoxos, 

2. Ophiuchiis and Hercules, 

3. Constellation Figures in an MS. of the 4th Century a.d., 

4. Diagram showing the Paths of Stars on the Star Sphere for Latitude 50°, 

5. Diagram showing the Stars Visible and Invisible for Latitude 50°, 

6. Diagram showing the Paths traced out by the Opposite Ends of the Earth's Axis owin 

the Equinoxes, 

7. Diagram showing the Path traced out by the Poles owing to Nutation, 

8. Diagram explaining the Aberration of Light, 

9. Diagram showing the Relative Proportion of the Proper Motion of Different Stars, 

10. Alterations in the Appearance of some of the Constellations, 100,000 Years hence, owing 

11. Diagram showing how the Actual Velocity of a Star is Calculated, 

12. Diagram showing how the Distance of a Star is Measured, ... 

13. The Comparative Sizes of the Sun and Sirius, 

14. Curves showing the Variation of Magnitude of Different Classes of Stars, 

15. The Milky Way as viewed with a Telescope, 

16. Diagram showing the Ratio of the Orbit of the Moon to the Diameter of the Sun, 

17. The Radiant Point of the November Meteors, 

18. Meteoric Stones, 

19. Diagram showing how the Orbit of the Moon is always Concave to the Sun, 

20. The Comparative Sizes of the Earth and the Moon, 

21. The Meridian Listrument of Eratosthenes, 

22. The Equatorial Astrolabe, 

23. The Ecliptic Astrolabe, 

24. The Parallactic Rules, 

25. The Refracting Telescope — (a), Galilean Telescope; (b), Old Refracting Telescope invented by 

(c). Modern or Achromatic Refracting Telescope, 

26. The Great Lick Refracting Telescope, 

27. Gregorian Reflecting Telescope, 

28. Cassegrainian Reflecting Telescope, ... ... ... ... ... 

29. Newtonian Reflecting Telescope, 
29a. The First Reflecting Telescope, made by Sir Isaac Newton, 

30. The Parallel Wire Micrometer, 

31. The Transit Instrument, 

32. The Field of View of the Transit Instrument, 

33. The Compensated Pendulum, ... 

34. The Equatorial Telescope, showing the " English " Method of Equatorial Mounting, 

35. A Modern Refractor Equatorially Mounted, 

36. A Modern Reflector, showing the " German " Method of Equatorial Mounting, 

37. Simple Spectroscope, 

38. The Author's Spectroscope, 

39. Altitude and Azimuth Instrument, ... ... .... 

40. The Sextant, 

41. Stands for Small Telescopes, ... 

42. Different Kinds of Eye-pieces, 

43. Diagram explaining the Different Symbols employed in the Star Charts, 



^Motion. 



Kepler 



LIST OF TABLES. 



->*«- 



The Actual Velocity of Stars, 

Ancient and Modern Positions of the more Conspicuous Stars, ... 

Binary Stars ; their Periods of Revolution, and the Magnitudes of their Components 

Different Classes of Stars, and the Principal Members of each Class, 

The more Important Comets belonging to the Solar System and their Periods of Revolution, &< 

The Apparent and Actual Lengths of the Tails of Comets, 

The Constellations, Ancient and Modern, 

The Constellations indicated in the Star Charts, and the Charts in which each occurs. 

The Length of a Degree of Latitude at Different Distances from the Equator, 

The Apparent Diameter of the Earth's Shadow in Lunar Eclipses, 

The Distances of the Vertex of the Lunar Shadow from the Earth in Solar Eclipses, 

The Distances of the Nearer Stars, their Annual Parallax, and the Time taken by their Light 

Earth, 
The Distances of the Planets from the Sun according to " Bode's Law," and their Actual Dist 
The Distance of the Sun according to Ancient Astronomers, 
]\[odern Determinations of the Sun's Mean Distance, ... 
The Eccentricity of the Terrestrial Orbit for 200,000 Years, 
Elements found in Meteorites, 
Elements known to exist in the Solar Atmosphere, 

The Elements from which Halley discovered the Periodicity of his Comet, 
SolarEclipses till 1900, ... 
Lunar Eclipses till 1900, 
Lunar Elements, 

The Principal Elements of the Planetary System for 1900, 
The Principal Elements of the Satellites of the Planets, 
The Equation of Time, ... .... 

The Greek Alphabet, 

The Diameters of the more Interesting Lunar Craters and Walled Plains, . . . 

The Principal Lunar Mountains, Seas, Gulfs, &c., 

Meteor Systems; their Periods, Duration and Time of Visibility, &c., 

The Lengths of Different Kinds of Months, ... 

Tlie Number of Stars of each Magnitude to the 20th, ... 

The Number of Stars of each Magnitude A^isible to the Naked Eye, 

The Observed Obliquity of the Ecliptic for nearly 3000 Years, ... 

The Old Method of Designating Star Magnitudes, 

Principal Facts about the Planets, ... 

Principal Pacts about the Sun, 

The Dimensions of Saturn's Rings, 

Sidereal Time at Noon for Different Dates throughout the Year, 

To Find the Time of a Star's Rising or Setting, 

The Magnitudes of Stars Visible with Telescopes of Different Apertures, ... 

The Apparent Time of Sunrise and Sunset at Different Latitudes and Dates, 

Catalogue of the Names, Magnitudes, and Positions of the more Important Stars for 1890, 

To Find the Stars Visible in the Northern or Soutliern Hemispheres at Different Dates and H 

To Find when a Star is on the Meiidian, 

Temporary Stars, and the Dates of their Appearance, ... 

Transits of Mercury, 

Transits of Venus, 

The Duration of Twilight at Different Times tliroughout the Year and at Various Latitudes, 

The Dividing Power of Telescopes of Different Diameters, 

The more Interesting Variable Stars, their Periods, and Range of Variability, 



in journey 



ances, 



ours. 



in" to the 



PAGE 

18 
14 
25 
23 
65 
67 
113 
118 
45 
87 



21 

51 

3.3 

34 

46 

71 

106 

64 

83 

84 

80 

61 

62 

121 

114 

79 

136 

69 

73 

29 

115 

47 

115 

62 

38 

57 

126 

126 

30 

120 

127 

122 

122 

27 

42 

44 

121 

111 

27 



"And is creation not a work of skill 
In its grand outline, in its parts minute, 
That we should mark its movements, trace its laws. 
Observe its fine consenting harmonies 1 " — Addison. 

"That which may profit and amuse is gather'd from the volume of creation, 
For every chapter therein teemeth with the playfulness of wisdom. 
* * * * * 

It is glorious to gaze upon the firmament, and see each distant shining world, 

To study Nature, and find her grand but simple secrets, 

The wonderful all-prevalent analogy that testifieth One Creator." — Martin Tupper. 

" Though still by them uncompreliended. 
From these the angels draw their power, 
And all Thy works, sublime and splendid, 
Are bright as iu Creation's hour." — Goethe. 



A POPULAR 



Handbook and Atlas of Astronomy. 



CHAPTER I. 
THE CONSTELLATION FIGURES— THEIR PROBABLE ORIGIN. 

" The names of the constellations of the zodiac have not been given to them by chance."— XapZace. 

STRONOMY is undoubtedly the oldest as well as the noblest of the 
sciences. Ever since man began to look beyond his everyday wants, 
he has cast an inquiring eye on the mysterious orbs moving above 
him. At an age in the world's history, long previous to that which saw 
the great dynasties of ancient Egypt, Babylon, Assyria, and Persia, 
springing into existence, semi-civilised man had not failed to notice and 
wonder at the magnificent panorama of nature revealed in the marvellous 
grandeur and the constantly altering appearance of the celestial sphere. 
The splendour of the " Orb of Day," the softer beauty of the " Queen of 
Night," the unaccountable movements of the "five wandering fires," the 
planets, and the countless hosts of smaller orbs of various hues and degrees 
of brightness, must in succession have attracted his attention, and awakened 
his most superstitious fears and fancies. To him the sun appeared as the 
great author of all things, and the stars as secondary powers, whose faces 
were covered at the approach of the sun-god's splendour. To him the con- 
stantly changing moon was a special mystery, appearing as a deity presiding 
over his destiny, warning hini of dangers to be encountered, and doing 
battle with the other heavenly powers on his behalf. In these superstitious fancies the so-called science of 
astrology, as well as many religious beliefs, had their origin ; for primitive man never seems to have cultivated 
the noble science of astronomy without connecting it with his own individuality and the secrets of the 
future. 

That this belief in the power of the heavenly bodies was in existence at a time when the great laws of the 
universe were unknown is not to be wondered at, and in one respect it had a beneficial effect, as it did much to 
stimulate an inquiry into the movements and nature of the various orbs. The moon, from its rapid motion 
among the stars, and the phenomenon of its phases, was in all probability the first heavenly body carefully 
observed, from which observation there woidd soon result the discovery of its true path round the star sphere, 
and the time occupied by it in making a complete revolution. The information thus obtained would gi\e rise 
to the invention of the first important time interval after the day — viz., a period of 28 days, or a complete 
sidereal revolution of the moon. This was probably the longest period of time mcasurcuient used by primitive 




Fig. 1. THE SPHERE OF EUDOXOS. 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



man, or the earliest conception of a year, traces of which are seen in uncivilised parts of the world even at 
present. As the motion of the sun among the stars requires much more observational skill to discern than does 
the motion of the moon, the former must have been discovered at a much later epoch. When once noted, it 
would, from necessity, suggest the idea of dividing the stars into groups or constellations. All along the solar 
track means would be required to indicate the position of the great orb from day to day, and these could 
only be arrived at by noticing the position of the sun among the stars, or the place occupied by the stars with 
respect to the rising and setting sun. At first the star zone through which the moon and sun appeared to 
move, seems to have been divided into twenty-eight nearly equal spaces, representing the daily movement of 
the moon. When, however, the sun's motion came to be detected, this division gave way to a more important 
one, a soli-lunar division — that is, one of only twelve spaces, resulting from a combination of the apparent 
movements of the two orbs. Accordingly each of the twelve parts into which the star zone was now separated 
would represent the space traversed by the sun in the interval occupied by the moon in making a complete 
revolution — each space corresponding to the amount of solar motion in an interval of about thirty days. Now, 
as each space would naturally be divided into thirty parts, the great circle of the heavens would thus come to 
be divided into 360 parts, and originate the division of the cii'cle into 360 degrees, and the ancient year into 
360 days. The constellations of the zodiac, then, were in all probability the first invented, these being at first 
simply a rude kind of calendar dividing the year into twelve parts, or months, and by the nature of the con- 
stellation figure, indicating, at the time when the sun was in its midst, what the particular month was noted 
for. After a time, when the gyratory movement of the poles of the earth, or the precession of the equinoxes 
(explained in Chapter II.), caused the zodiacal constellations no longer to coincide with the solar calendar, the 
original use of the zodiac became lost, and its various figures, along with new constellations invented from 
time to time, became part of the elaborate systems of mythology and religions, a fact to which the existence of 
the Sphinxes {Leo and Virgo), Winged Bulls {Taurus), Rams {Aries), &c., bears testimony. 

The above, however, tells us nothing of the age or the country in which the figures of the constellations 
were invented. That the country in which this important work of dividing that portion of the star sphere 
annually traversed by the sun into groups characteristic of the principal events taking place throughout the year, 
was entirely or almost cloudless, is certain, and several countries could be mentioned which meet this condition, 
as Egypt, Assyria, &c. But at what epoch it was commenced is not so easily decided. Even after minute 
research, it must be confessed it is only with great difficulty and caution that anything in the way of a date 
can be suggested. Reliable history does not carry us so far back as to throw any light on the subject, and, 
if the question is to be decided at all, it must chiefly be from the testimony of the star groups themselves. 

When one examines a modern chart of the heavens, with the constellation figures thereon depicted, it is 
found that there are many, for the most part unimportant, groups of stars, which must have been named at a 
comparatively recent date, such as Sextans, Octans, Pavo, Indus, &c. These, however, it is necessary to 
remove from the chart, so that the older figures can be seen to the greatest advantage. This has been done in 
Plates 1 and 2, which contain only what are known to be old constellation figures. In many cases, the 
names of the old groups have been changed by the various nations by whom they have been handed down to 
us, but, fortunately, this change of name is not of so much consequence, as their characteristic forms seem 
to have, for the most part, remained unaltered. Thus the Greeks, who are believed to have received the 
constellations from the ancient Egyptians, gave to each a Grecian name, while they retained the idea belonging 
to the group. The discovery at Rome of a sculptured marble globe of the heavens resting on the figure of 
Atlas {see Fig. 1) proves this to have been the case. On this sphere, which is the oldest known reijresentation 
of the heavens, and believed to be an exact copy of the celebrated sphere of Eudoxos, the various constellations 
are clearly depicted. Now, we know that Eudoxos, before constructing his celebrated star globe, travelled 
into Egypt about the year 380 B.C., and received astronomical instruction from the priests there. This 
iaslruction, combined with his own observations, enabled him to write two important works, showing the 



PL ATI 




Northern Hemisphere, 



The Old Cons 



SiD 2. 




Southern Hemisphere. 



TioN Figures. 



THE CONSTELLATION FIGURES—THEIR PROBABLE ORIGIN. 



connection between the weather and the different positions of the constellations in the sky — viz., the 
Phainomena, or " Appearance," and the Enoptron, or " Mirror of Nature." Unfortunately, however, for 
astronomical science, these works of Eudoxos have been lost, and all the information we have of them is from 
one of the most popular of ancient works, the poem of Aratos, written about a century after the time of 
Eudoxos. As Aratos possessed no astronomical knowledge himself, he seems to have faithfully followed the 
description of the constellations given in the Phainomena, and thus his celebrated poem can be little more 
than a versification of the work of Eudoxos. In this poem, which must have been familiar to St. Paul, as 
he quotes from it, there is given a fairly minute description of the various constellation figures, and, at the 
same time, mention is made that these figures were invented in some very remote age antecedent to the time 
of Eudoxos.* 

The oldest known records of the constellations only carry us back to about the year 400 B.C. ; but 
their invention is undoubtedly much older, and was known to the Egyptians and Chaldeans long before that 
time. From the supposed connection between the Great Pyramid of Cheops and several of the star groups, the 
epoch of the construction of that building — about 2000 B.C. — has been thought by some to be identified with 
the division of the heavens into groups. But though, for astrological purposes, several of the constellations may 
have become connected with the Great Pyramid, it seems that the origin of the present arrangement of the 
zodiac is very much older. Others, again, have tried to connect Chaldea with the invention of the constella- 
tions, and they fix upon nearly the same epoch as that already mentioned ; but while Chaldea and Assyria 
have undoubted historical claims, on account of their connection with very ancient astronomy, yet Egypt seems 
to be the country in which the zodiac at least was known at a very distant age. This we need not wonder at, 
as, of all countries in the world, Egypt seems at a very early time to have reached a high state of civilisation. 
At the time of Herodotus, 500 B.C., for instance, the Egyptians were more advanced in culture than any other 
people, and were considered to be the most ancient nation. From the priests, philosophers, and artisans of 
Thebes and Memphis, the countrymen of Hesiod and Homer received instruction in religion, science, and 
arts, and derived the groundwork from which was built up their elaborate system of mythology. From 
Egypt the Greeks learnt the system of writing history, as in that country, from the very earliest times, it had 
been the custom to transmit to posterity the records of past events. The Greeks also received many of their 
architectural ideas from the same people, and these ideas have never been surpassed for sublimity and 
grandeur of conception. Still further, it was from the philosophers of the Nile that Thales, six hundred years 
before our era, received the knowledge by means of which he was enabled to calculate eclipses, to determine 
the equinoctial and solstitial points, and to instruct his countrymen in the method of navigating their ships by 
observations of the stars. But even before Greece was in existence, the valley of the Nile was peopled bj' a 
highly civilised race, and this race, four thousand years ago, had made such great progress in the arts as 
enabled them to construct buildings which for size and grandeur have been the wonder of every subsequent 
age — a fact which points to a great antiquity, as this perfection could only have been the outcome of an 
advanced knowledge of the sciences, derived from the combined study of numberless generations. 

It will not, then, be at all surprising if in our inquiry we are led to believe that the "land of the 
Pharaohs " was more or less connected with the figures of the constellations, at a time when other countries 
must have been in a state of barbarity. Owing to the precession of the equinoxes, the poles of the earth are 
made to point successively to various parts of the star sphere throughout the long period of about twenty-six 



* " Some man of yore 
A nomenclature thouf,'ht of and devised 
And forms sufficient found. For men could not 
Or tell or learn the separate name of all : 
Since everywhere are many, size and tint 



Of multitudes the same, but all are drawn arouncL 
So thought he good to make the stellar groups, 
That each by other lying orderly, 
They might display their forms. And thus the stars 
At once took names, and rise familiar now.' 

See Translation, by Robert Brotcn. 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



thousand years. This produces a slow apparent movement of the stars, and a displacement of the constel- 
lation figures in the heavens ; accordingly many of the imagined figures in the sky, which in ancient times, 
and at the time of their invention, appeared to be in their natural posture, are now considerably altered in 
position, and in some cases completely inverted. The constellation of Hercules {see Fig. 2) is a striking 
example of this processional effect.* When this figure was invented it could not have been situated as it 
now is, but, as described in the poem, kneeling, with the head upright. Now, as Ophiuchus appears to 
be quite as ancient as Hercules, it also would be in an upright position, and as the head of the figure is 
close to the head of Hercules, and the body extending in the opposite direction, these constellations could 
only be seen in their true positions when the heads of the figures were near the zenith of the place from 
which they were viewed, the one constellation appearing upright to the north, tbe other to the south. This 

arrangement could only have taken place in a 
latitude of about 25 degrees north — the latitude 
of ancient Egypt. Again, the constellation of 
Pegasus is at present seen in an inverted posi- 
tion ; so also are the constellations of Andromeda, 
Cassiopeia, &c., but in the past in the latitude 
of Egypt they were seen in more natural posi- 
tions near the zenith, as in Plate 1. From the 
an-angement and the present positions of the old 
constellations, one is thus led to infer that it is 
to the ancient Egyptians we are indebted for the 
first division of the stars into constellations. 
When, however, we come to the arrangement of 
the zodiac, v/e see how intimately connected 
these constellations are with that most interest- 
ing of countries. 

We have shown that the zodiac must origin- 
ally have been employed as a division of the solar 
year into twelve parts, the individual constella- 
tions representing, in all probability, the season 
of the year, the nature of the prevailing weather, 
or the principal occ^^pation at the time when 
each group was in conjunction with the sun, or 
when the solar orb Avas passing amongst its stars. 
For the constellation figures do not seem to have 
been suggested by a resemblance of the various 
star groups to familiar objects, because in most 
cases they have no resemblance whatever to the object named, but each of the old groups was identified with 
objects typical of what was continually taking place either in the heavens or on the earth ; in particular 
with the struggles, victories, and defeats of the " Great Sun God," in his encounter with the evil powers 
of darkness, while performing his annual journey round the star-sphere. If this, then, be the object for 




Fig 



OPHIUCHrS AND HERCULES. 



* In the poem of Aratos this constellation is well 
described : — 

" Like a toiling man, revolves 
A form. Of it can no one clearly speak, 
Nor to what toil he is attached ; but, simply, 



Kneeler they call him. Labouring on his knees, 
Like one who sinks he seems ; from both his shoulders 
His arms are raised ; each stretching on its side 
About a full arm's length. And his right foot 
Is planted on the twisting serpent's head." 



THE CONSTELLATION FIGURES—THEIR PROBABLE ORIGIN. 



which the zodiac was invented, one would expect that its constellation figures would be strikingly 
representative of some particular country, and if of Egypt, they would be intimately connected with 
the Nile ; for from the remotest antiquity Egypt has been considered as solely dependent on tliat 
great river, as, from the regular overflow of its water, this country is in reality the " Gift of the Nile." 
This the ancient Egyptians fully recognised. They said : — 

" Hail to thee, Nile : 
Thou showest thyself in this land, 
Coming in peace, giving life to Egypt."* 

Egypt, then, without the Nile is nothing, for without the regular inundations, it would be like the 
immediately surrounding country, partly a sandy waste and partly a rocky desert, and could not in the past 
have played so important a part in the world's history as it has undoubtedly done. Only by the presence of 
the river flowing from the mysterious regions of the south was Egypt fertilised. Annually it conveyed to the 
multitudinous inhabitants dwelling on its banks, great agricultural wealth ; produced a salubrious climate, and 
at the same time beautified the landscape. Therefore we would expect that, if the zodiac were an Egyptian 
invention, many of the constellations of which it is composed would be more or less directly connected with 
the yearly rise and fall of this great river. Indeed, this seems to be the case, for, when due allowance is made 
for the gyratory motion of the earth, or the precession of the equinoxes, the principal events which took place 
in ancient Egypt throughout the year, and their duration, are fully explained. 

In ancient Egypt, the solar year is believed to have commenced with the lower, or winter solstice, which, 
though corresponding to our winter, was the time immediately following the sowing of the seed. At our 
spring, three months afterwards, when the sun was crossing the vernal equinox, the harvest took place, and 
this was followed by the valuing of the crop and the payment of tribute. During the two months preceding 
the summer, or higher solstice, the most unhealthy season and the greatest climatic disadvantages were 
experienced. For no less than fifty days, as is the case still, the Ichamsin,'\' or deadly south wind, prevailed, 
bringing with it disease and death ; for if the plague appeared throughout the year it was during that interval. 
About the middle of our June, or near the time of the higher solstice, the Nile, in ordinary seasons, began to 
rise, and continued steadily to do so, till by the beginning of August the overflow occurred. Three months 
after the commencement of the rise, towards the end of September, at the time of the descending or autumnal 
equinox, the inundation reached its highest, when, according to Herodotus, the whole " Delta " was converted 
into an inland sea, whose towns and villages appeared dotting the surface like so many islands. From this 
time the fall rapidly took place, and in little over one month from the maximum overfow, or towards the 
close of October, the waters had so far subsided as to again be confined to their original channel, and once 
more the Nile appeared. The waters having now subsided, and having by their presence deposited a valuable 
coating of soil, thereby giving to the land a greater fertility than the richest manure could have imparted, 
the country was, during the next month — corresponding to our November — put under culture, and, by the 
second month of the year, or February, covered with green and luxuriant crops. 

The above-mentioned events, which took place throughout the year in ancient Egypt, are fully explained 



" Hail to thee, Nile : 
Thou showest thyself in this land, 
Coming in peace, giving life to Egypt. 

* * * * 

inundation of Nile, offerings are made to thee ; 
Oxen are slain to thee ; 
Great festivals are kept for thee ; 
Fowls are sacrificed to thee ; 
Beasts of the field are caught for thee ; 



Pure flames are offered to thee ; 
Offerings are made to every god, 
As they are made unto Nile. 

* * * * 

Shine forth, shine forth, Nile ! shine fortli ! 
Giving life to men by liis omen ; 
Giving life to his oxen by his pastures ! 
Shine forth in glory, Nile ! " 

Sec Rawlinson's " Egijpt" 

t Khamsin is an Arabic word meaning fifty. 

B 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



by the zodiacal constellations, if we move them backwards to the apparent positions they occupied at the 
distant epoch of between fourteen and fifteen thousand years ago, or at the time when the brilliant star Spica 
was near the vernal equinox. To many this may appear as too far back to be accurate, yet no other epoch 
will explain the zodiacal calendar of ancient Egypt, and even a difference of only one thousand years either 
way makes a considerable alteration in the coincidences. At the distant epoch already mentioned, the 
constellations, owing to the precessional movement of the earth which has since taken place, were occupying 
a position in the sky nearly diametrically opposite to that in which they at present appear (see Plate 3). 
Capeicornus, for example, instead of being where it now is, near the lower solstice, was then on the higher, or 
summer solstice ; while CANCER, instead of occupying, as now, nearly the highest point in the ecliptic, was then 
situated at the lowest part of the sun's yearly course. The equinoctial constellations were reversed in a like 
manner — ViRGO occupying the vernal, and PiSCES the autumnal equinox. The harvest, we have seen, being 
near the time of the sun's crossing the equator, when ascending, or in our spring, this luminary was thus, during 
the time of harvest, travelling among the stars of what has long been considered as a purely harvest constella- 
tion, — viz., Virgo, the Virgin, who, as mentioned by Aratos, " carries in her hand the brilliant ear of corn " (the 
star Spica, see Plate 2). The next constellation, or Libra, though believed by many to be a more recent inven- 
tion than the other zodiacal constellations, seems also to be intimately connected with the harvest, or the 
ingathering of the grain. This constellation figure has been explained by some as originally representative 
of justice, or as a sign of equality, invented at the time when it was situated on the autumnal equinox, when 
the days were equal to the nights, or when there was a balance of light and darkness. Others have 
even held that it is of very recent date, there being originally only eleven zodiacal constellations. There 
is evidence, however, that such is not the case, but that it is as ancient as the others, and, coming as 
it does immediately after the " Gleaning Maid," the constellation of the Balance seems more reasonably 
to be representative of what undoubtedly then took place during the time the sun was passing through 
the stars composing it — viz., the balancing month — the month in which the grain was weighed and 
valued, when the amount for tribute or tithes was probably laid aside. 

After Libra come the constellations of Scorpio and Sagittarius — constellations which fully explain 
what took place during the two months preceding the summer solstice. As the sun at that distant time 
entered the scorpion's claws, his long struggle would commence with what to the Egyptians Avould be the 
power of evil. At this very time the fatal winds began to blow from the south, bringing with them 
death and destruction. The sun, at intervals shorn of his beams, and often nearly obscured by the amount of 
fine sand blown from the desert, had the appearance of struggling with the powers of darkness. The god of 
the river, too, would seem to have withdrawn his beneficent power, as the waters of the Nile were then at 
their lowest. Scorpio, then, which has always been considered as symbolical of evil and darkness, the con- 
stellation that was considered cursed by the ancients, would indeed be typical of the then prevailing power;* 
for the winds did not cease until the sun had passed from amongst its stars, and entered those of Sagittarius, 
which very suggestively represents the solar hero, shooting his arrow, or his beams, at the scorpion's heart, 
and finally triumphing over the power of evil.-J- {See Plate 2). 

From Sagittarius, the sun, in his upward and triumphant course, would now enter the constellation of 
the Goat, or Capricornus, at the time when his highest point, the summer solstice, was reached. In the time 
of Eudoxos this constellation occupied nearly an opposite position, or was situated at the winter solstice, as 
Aratos mentions " where retrogrades the solar might." With more truth, however, the words may be applied 
to the position in which it was placed at the distant epoch already mentioned, for is it not certainly a climbing 

* The Akkadian word for this constellation means " the Seizer-and-Stinger," and also " The-Place-where-one-bows-down," 
both of which meanings clearly indicate the supposed nature of, and effect produced by, the constellation. 

t In the cuneiform inscriptions Sagittarius is designated "the Strong one," the "Giant king of war," and the " Illuminator 
of the great city " ; titles which are strikingly representative of the sun when overcoming evil, or darkness. 



THE CONSTELLATION FIGURES— THEIR PROBABLE ORIGIN. 



animal, grazing not in the lowland regions, but in the rocky heights of the mountains ? Accordingly the 
original position of Capricornus could not have been where it now is, near the lowest part of the sun's apparent 
annual course, but at the position it occupied fifteen thousand years ago — viz., the higher solstice, representing 
the sun as having reached his highest point in the heavens. In examining the constellation figure on Plate 2, 
it will be noticed that the celestial animal is totally unlike a true capricom, in respect to its having a fish's 
tail. This is no comparatively modern addition, as it is not only given on a MS. in the British Museum, 
supposed to belong to the second century of our era (see Fig. 3), but the amphibious nature of the creature 
has been discovered on an excavated Babylonian stone.* The meaning of this rather curious appendage has 
not, as far as I am aware, been suggested by any previous writer. The explanation, however, seems to be a very 
simple one when we consider the position the constellation occupied at the time mentioned. At that time the 
stars forming the fish's tail of the goat, marked the sun's position at the exact instant the Nile hegoM to Hse, 
when the sun was beginning to descend from the highest point, and, as a deity, to exert his mighty influence on 
behalf of the rising waters.-}- This supposition is remarkably borne out by the next constellation, or AQUARIUS, 
the Water-Bearer — which, as will be seen in Plate 2, overlaps to a large extent the fish's tail. This 
constellation, like the others previously noted, is also typical of the principal event which took place in ancient 
Egypt.J As the sun advanced into the constellation of the Water-God (Aquarius), its influence produced the 
steady rise of the river, until by the time he had reached that part of his course which is marked by the stars 
representing the mouth of the vessel from which Aquarius pours out the water, the Nile had, in ordinary 
seasons, risen to such a height that its waters were literally " poured out over the land." This is no idle 




Fig. .3.— Constellation Figures in an MS. of the Second Century a.d. 

imagination, but an actual fact, which undoubtedly took place in Egypt at the time we mention, and the 
surrounding constellations, instead of contradicting the hypothesis, only lend their aid to confirm it in a 
striking manner. Near Aquarius, for instance, is the Southern Fish, swimming in the stream, and the dreaded 
" sea monster " (Cetus), plunging in the now really " deep waters " ; while the next zodiacal constellation, 
Pisces, is symbolical indeed of the season, when, owing to the complete flooding of the land, fish would be 
easily and plentifully obtained. 

At this time, as already mentioned, PiSCES embraced the autumnal equinox, extending exactly to the 
position which the sun reached when the inundation was greatest. From this moment, as the sun pursued 

* According to Prof. Sayce the Euphratean name, found on the cuneiform inscriptions for the month occupied by Capricornus, 
is the " Father of Light," and he remarks, " It is ditlicult to understand how it can have been called a month of light." This, 
however, is fully explained by the position occupied by the constellation as above indicated. Whilst the sun, as already mentioned, 
was traversing the constellation of the Goat, the days were longest and illuminated to the fullest extent, so that this period w;ia 
truly a "month of light," which it could not have been at any other epoch than that of about 15,000 years ago. 

t The Egyptian god of the waters, " Chnnm " is, curiously enough, represented \\ith goafs horns (not ram's horns>— thus 
showing the intimate connection between Capricornus and the rising of the Nile. 

X The Akkadian meaning for the month occupied by Aquarius is " The Lord of Canals." As revealed by the brick 
tablets, the constellation is also intimately connected with the Deluge. 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Lis zodiacal course, the waters began rapidly to retire, and in less than one month afterwards, or by the time 
the sun had passed through the constellation of Aries, the water had subsided to so great an extent that sheep 
and other animals could once more in safety be sent out to pasture — when probably a ram, as representative 
of the leader of the flock, was sacrificed.* The sun, too, when in this position, was directly over the end of 
the long winding constellation, Eridanus, the River, which in all probability represents a duplication of the 
Water-God, if not of the Nile itself (see Fig. 3) ; for, when the sun was in this position, the Nile, which for 
nearly three months had been lost in the flood, had now^ so far regained its original channel as to be once 
more visible. Above Aries, too, is the very old constellation of the Triangles, which has always been connected 
with the Delta of the Nile; and with good reason, for the sun was in conjunction with the Triangles when 
the various land-marks destroyed by the inundation would require to be renewed, or the land triangulated 
and measured, from which necessity, in all probability, originated the science of geometry. 

The sun now entered the constellation of Taurus, and continued there during the month corresponding 
to our November, which, in ancient Egypt, was the month when the land was put under cultivation, and 
the oxen yoked to the plough. In this constellation is the well-known and very ancient group called the 
Pleiades, mentioned by Aratos as the Clusterers. These always seem to have been intimately connected with 
agriculture.-f- From Taurus, the sun next passed into the constellation of Gemini, the Castor and Pollux of 
the Greeks, but mentioned in Aratos only as the Twins, and known to the ancient Egyptians simply as a pair 
of kids, to the Chaldeans as a pair of gazelles, and to the Arabians as a pair of peacocks. This, in all 
probability, at the epoch we refer to, marked the lambing season, and Auriga seems to be in some way 
connected, as the figure of the so-called charioteer has always been represented as holding kids in his arms.j 

In moving out of Gemini, the solar orb next entered the dark and gloomy constellation of Cancer, the 
Crab — which, from its faint stars and dark appearance, was very anciently looked upon as typical of the 
powers of darkness. Like nearly all the constellations in the heavens. Cancer bears no resemblance w^hat- 
ever to the object it is supposed to represent, but received its character simply from what usually took place, 
either on the earth or in the heavens, when the sun moved among its stars. Hitherto it has been supposed 
by many that at the time Cancer received its name, it occupied the place of the higher solstice, for, as crabs 
appear to walk backwards, this creature was thought very fitly to indicate that part of the sky where the 
solar retrogradation occurred ! This, however, would only give an epoch of little more than two thousand 
years ago, a date, undoubtedly, too recent, and quite within historic times. But the constellation of Cancer is 
far older, and was evidently known to the Egyptians in very ancient times. The Egyptians, as is well known, 
do not seem to have been very familiar with the crab, but they had a creature somewhat similar, and to them 
vastly more important — the celebrated Scarabaeus, an insect of the beetle species.§ By them this creature 
was treated with the greatest reverence, as is shown in the Temple of Edfou, where there is to be seen 
sculptured on the walls priests paying Divine honours to it, as symbolical of the sun. What, then, would be 
more natural than that it should occupy a prominent position in the celestial calendar of a people in whose 
eyes it was exceedingly sacred ? At that epoch already mentioned the constellation of the Scarabaeus 
(Cancer) w^ould indeed occupy the most prominent position in the Egyptian zodiac ! It would mark, indeed, 



The Assyrian word for the month occupied by Aries is the "Altar" and the "Sacrifice." 



" The Flock of Clusterers. Not a mighty space 
Holds all, and they themselves are dim to see. 
And seven paths aloft men say they take, 
Yet six alone are viewed by mortal eyes. 
From Zeus' abode no star unknown is lost 
Since first from birth we heard, but thus the 
tale is told ; 



These seven are called by name Alkyone, 

Kelaino, Merope, and Sterope, 

Seygete, Elektre, Maia Queen. 

They thus together, small and faint, roll on, 

Yet notable at morn and eve through Zeus, 

Who bade them show when winter first begins, 

And summer, and the season of the plough. " 



X Gemini may also have been connected with the birth of a new year, which was supposed to be brought about by the 
Influence of the twin deities, the Sun and Moon. 

§ In a MS. of the twelfth century the constellation figure of Cancer is represented by a creature somewhat like a water-beetle. 



THE CONSTELLATION FIGURES— THEIR PROBABLE ORIGIN. 



the lowest, and most critical part of the sun's apparent yearly path (see Plate 3).* For when the sun entered 
this dark constellation, the days would not only be shortest, but the fight with darkness greatest. Was their 
god, whose presence brought life and happiness, intending to sink lower in the heavens, and leave them alto- 
gether ? would be the anxious question of the ignorant and superstitious masses of a sun-worshipping nation ; 
or would he, after reaching his lowest point, begin once again to mount upwards, and for another year repeat 
his encounters with the powers of evil ? Now, to the Egyptians the Scarabaeus was not only a very sacred 
creature, but at the same time a creature representative of the resurrection, or the continuance of life. So 
that they had very appropriately indicated their first month of the year by placing in the heavens the sign of 
continued life, exactly in the position where their sun-god moved when his struggles for the time were over, 
and his power restored, as it were, by beginning the ascent into the heavens. 

After Cancer comes the last of the twelve zodiacal constellations we have to mention — Leo, the Lion. 
That this constellation should occupy the position it does in the zodiac is not at once so clear, as the lion does 
not specially belong to Egypt. But though this is the case, it is certainly African, and was therefore not 
unknown to the ancient inhabitants of the Nile Valley. It was perhaps owing to its rarity that it came to be 
looked upon as a somewhat sacred animal, and introduced into the zodiac, to which the Sphinx, a purely 
Egyptian conception, seems to testify ; the Sphinx being simply a combination of two constellation figures, 
Virgo and Leo, and likely to have been invented at about this epoch, as these constellations then occupied 
the most important part of the ancient star sphere, the vernal equinox.-f- When the sun, then, was moving 
through Leo, the crops were beginning to ripen, and the solar hero of the Egyptians was once more appearing 
in all his strength and power, like a lion, as he approached the equinox ascendingly — that triumphal crossing 
point which divided the celestial sphere of the ancients into the two important hemispheres — the lower, a 
region of death and darkness ; the higher, a region of life and light.| Thus, Leo is in all probability but 
another type of the sun ; the sun in all his strength, which like a lion is prepared to spring on Hydka, the 
Great Water-Snake, beneath — symbolical, again, of the power of darkness. The most vital portion of the 
latter creature, the head, has been well placed, where the struggle was fiercest — i.e., when at the lowest part of 
his course, or under the constellation of the Crab (see Plates 1 and 2). When, however, the sun climbed into 
Leo, the triumph commenced, and by the time he had reached that part of his path which lies directly above 
the tail of Hydra, the victory was accomplished, the great orb had crossed the Equator, and travelled into 
the region of light ! Such, then, were the struggles which the solar deity of the ancient Egj'ptians had to 
encounter in his yearly movement round the star sphere. The seemingly meaningless constellations of the 
zodiac are thus, in the most natural manner, fully accounted for. 

As already suggested, many of the ultra-zodiacal constellations seem to be duplications of those compos- 
ing the zodiac. For example, immediately above Scorpio and Sagittarius, as representative of the sun's 
struggle with the evil power, is Ophiuchus and Serpens — the Serpent-Bearer and the Serpent — which is very 
evidently symbolical of the solar hero, standing upright and triumphant, firmly holding the vanquished though 
still struggling serpent — the ancient representative of evil (see Fig. 2). The same idea is again brought out in 
the constellations lying directly underneath, or to the south of Scorpio — in Centaurus, a solar hero, and Lupus, 
a type of darkness — the latter, however, being a comparatively modern name for an ancient and similar character. 

The harvest constellation of the Virgin seems also to be duplicated, for above it is Bootes, the Ploughman, 

* The original position of Cancer, near the lower, or southern solstice, is clearly proved by the meaning of the Akkadian 
word for the month occupied by the constellation — viz., " The Sun of the South " or the " Southern Sun." 

t The Egyptian goddess " Sechet " or " Pasht " appears simply to be the Sphinx, as she is always represented with a lion's 
head. The connection between the Sphinx (Leo and Virgo) and Hydra is indicated by the goddess ha\'ing the sun's disc and 
snake on her head. 

X According to Macrobius "This beast seems to derive his own nature from that luminary (the Sim), being in force and 
heat as superior to all other animals, as the sun is to the stars. The lion is always seen with his eyes wide open and full of fire, 
so does the sun look upon the earth with open and fiery eye." 



10 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



or rather harvester, symbolical of the harvest, which was being reaped during the time of the sun's passage 
beneath the constellation. Aquila, again, one of the very old constellations, being placed above Capricornus, 
would, at the epoch mentioned, be situated directly above the higher solstitial point, and be symbolical of the 
sun's highest flight.* This is strikingly corroborated by the old drawings of this constellation figure, which, 
instead of showing the eagle flying downwards, as in Plate 1, indicates the celestial bird sitting upright, and 
apparently perched on some high mountain peak (see Fig. 3), at once suggesting the idea that it is representa- 
tive of the sun having reached his highest point in the heavens. Following Aquila is the small, though very 
ancient constellation of Delphinus. This constellation being situated immediately after the higher solstice, 
very fitly indicates the direction of the descending course of the sun ; which, like a dolphin having ascended, 
will now descend, or re-plunge beneath the wave. In Eridanus, as already indicated, we have, in all proba- 
bility, a duplication of AQUARIUS, the Water-God, as representative of the Nile; in Cetus and Perseus, 
another fight between the powers of light and darkness ; and in the young goats, in the constellation of 
Auriga above Gemiki, a duplication of the zodiacal constellation of the twin kids. The brilliant star Sirius 
(Canis Major) and the magnificent constellation of Orion, seem also to have been used at the date already 
mentioned. Sirhis, the " Blazing Dog-Star " is known to have always been intimately connected with the 
Nile. The position it occupied at that date was such that its appearance announced the rising of the river ; 
and thus it was symbolical of a faithful dog warning the Egyptians to be on their guard. But its use did not 
stop here, for, by its I'egular appearance, the length of the old Egyptian year was determined. 

The above appear to be the principal ultra-zodiacal constellations connected with the epoch of about 
15,000 years ago. Several of the others are probably quite as ancient, but, on the other hand, may have been 
of comparatively recent date. In fact, one could scarcely expect that even the principal groups, outside of the 
zodiac, would receive names and characters at the same time, but that the completion of dividing the visible 
star-sphere into constellation figures would be the result of the studies of several generations. Indeed, there is 
evidence that several of the constellation figures were invented at the epoch of only 4000 years ago, and in a 
latitude slightly different from that of Egypt ; but those that have been mentioned, from their positions in the 
heavens, seem to have been known long before that time in the region of the Nile, or to the ancient 
Egyptians. 

Of course it may be urged that the same coincidence took place at a much more recent date, when the 
sun, instead of being in conjunction with the star group, was exactly opposite to it, or when the group was 
seen high on the meridian at midnight. This would certainly be the case after one half of a precessional 
revolution, 13,000 years later, or 2000 years ago. From historic evidence alone, however, this date is known 
to be far too recent ; besides, as is well known, the ancients never followed this method. A star, or constellation, 
was supposed to have power only for good, or evil, when its influence was added to that of the solar orb, not 
when in opposition to the sun, or seen in the heavens at midnight. Astrologers regarded the star groups in 
the same way, so there is every reason to believe in the more remote date, distant though it is, as having been 
the time when many of the constellation figures were invented by the highly civilised, and certainly the most 
remarkable people the world has seen — the ancient inhabitants of the Nile Valley. 

* The ancient Egyptians considered the hawk as sacred, and symbolical of the sun. Their sun god Horus, the son of Osiris, 
is always represented with an eagUs head, surmounted by the sun's disc ; and in the Egyptian temples the deity's omnipresence 
is symbolised by outspread eagle's wings. 



Plate 




CHAPTER II. 

MOVEMENTS OF THE EARTH WHICH AFFECT THE APPEARANCE OF THE HEAVENS. 

" The planet Earth so stedfast though she soeiii, 
Insensibly three different motions move." — Milton. 

DIURNAL MOTION. 

The least attentive observer cannot fail to have noticed that during each day every celestial object appears 
above the eastern portion of the horizon, mounting into the sky until it reaches its highest point on the 
meridian, then gradually sinking and approaching the horizon, where finally it disappears towards the west. 
This is owing to the well-known apparent diurnal, or daily movement of the star-sphere from east to west, 




Fig. 4. diagram showing paths of stars on the 

STAR sphere for LATITUDE 50°. 



Fig. 5. diagram showing stars visible ani> 
invisible for latitude 50°. 



produced by the rotation of the earth on her a.xis in the opposite direction. During each interval of 2o hours 
56 minutes 4 seconds our globe makes a complete rotation, and turns the observer successively towards every 
celestial object. All bodies on the celestial sphere thus appear above his horizon, and move in a westerly 
direction, describing, throughout a complete revolution, true circles round two apparently fixed points in the 
heavens, which are directly above the poles of our globe. 

Each object, however, does not pursue the same apparent diurnal path. Those, for instance, situated 
midway between the poles of the heavens or near the celestial equator, rise exactly in the east, and set due 
west, All objects, on the other hand, south of the equator, rise, in proportion to their distance from that great 

11 



12 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



circle of the heavens, to the south of the east, and set to the south of the west ; and those to the north, rise 
and set at places on the horizon from the east and west also in proportion to their positions with respect to 
the equator {see Figure 4). All stars whose distances from the pole elevated above the horizon of the 
observer are less than his distance, in degrees, from the terrestrial equator, never set at all, but are 
alwaj's above the horizon, and become visible shortly after sunset ; while those situated within the same 
distance from the opposite or depressed pole never rise, and are in consequence always invisible. Thus 
in Britain all stars whose distances from the North Pole are less than 52 degrees, as in Figure 5, never set, 
but apparently revolve round the Pole in a direction opposite to that of the movement of the hands of a watch; 
while, on the contrary, those stars distant from the South Pole less than 52 degrees are never seen in Britain, 
being constantly beneath the southern horizon (see Fig. 5). 

From the apparent diurnal movement of the star-sphere, the appearance of the heavens is constantly 
altering. Star-group after star-group is caused to disappear in the west, while in the opposite part of the sky, 
towards the east, new groups are brought into view ; and thus a constellation that appears high up in the sky 
will, a few hours afterwards, be low down on the western horizon, or have entirely disappeared. 

ANNUAL :\rOTION. 

But while the stars are apparently carried daily round our globe as a centre, they seem also to travel 
round once every year. Each day if a particular group of stars be watched, it will be found that it rises and 
sets sooner than on the previous day, thus apparently moving towards the west, until it gets lost in the sun's 
rays. A constellation, for example, that on a particular day is seen near the meridian at midnight, will, three 
months afterwards, be seen in the same position six hours earlier; six months afterwards, twelve hours sooner; 
nine months afterwards, eighteen hours sooner ; and in the course of a year be again on the meridian at mid- 
night. This apparent movement, to which all stars are subjected, is the outcome of the earth's annual 
journey round the sun. From this revolution of our globe, the sun is apparently caused to move among the 
stars to the east, thus producing an apparent forward movement of the constellations to the west, or towards 
the sun. Now, as our day, or time, is determined by the return of the sun, he thus seems to be stationary, 
v\rhile the stars are apparently carried round the earth once every year, or exactly in the time occupied by our 
globe in making a complete revolution of its orbit. The stars, then, occupy positions in the sky with respect to 
the sun, depending on the position of the earth in her orbit, or on the season of the year. This is why some 
constellations are seen only at certain seasons, for a group of stars can only be visible when somewhat distant 
from the sun, so as to appear above the horizon before sunrise or after sunset. The zodiacal constellation of 
Gemini, for instance, cannot be seen at the beginning of July, for the sun is then directly between us and the 
group ; but the zodiacal constellation that is diametrically opposite to it — Sagittarius- -will be on the meridian 
at midnight, a position that the Twins cannot occupy till the beginning of January, when the sun is then 
apparently moving among the stars of the ARCHER. Therefore while the diurnal rotation of the earth is 
turning the observer to different parts of the star-sphere, and constantly altering the appearance of the 
heavens from hour to hour, the annual movement of our globe round the sun is changing the aspect of 
the heavens from day to day at the same hour. For the purpose of easily following these two important 
apparent motions from any part of the globe, the twenty-four different views or circular maps, inserted 
at the end of the volume, have been constructed. 

gyratory motion, or precession. 

The diurnal and annual motions are the two principal apparent movements of the star-groups, and were 
known from very ancient times. There is, however, another motion of the earth sensibly affecting the appear- 
ance of the heavens, which was not discovered till about the year 120 B.C. Hipparchus, by comparing his own 



MOVEMENTS OF THE EARTH WHICH AFFECT THE APPEARANCE OF THE HEAVENS. 



13 



observations of the positions of the stars with those made 180 years previously by Timocharis, discovered 
that they were slowly travelling round the celestial sphere in paths, which, unlike those described by the 
stars in the daily and yearly movements, were not parallel to the equator, but to the track traced out by the 
apparent annual movement of the sun, and in the same direction. This is now known as the Precession of tlie 
Equinoxes, first truly explained by Copernicus, and physically accounted for by Newton, as being produced by 
the attractive action of the sun and moon on the spheroidal figure of the earth in endeavouring to cause the 
terrestrial equator to coincide with their own, the ecliptic plane. This action causes the equinoctial points, or 
those places where the equator crosses the sun's apparent annual path — places occupied by the sun every 20th 
of March, and 22nd of September — to slowly proceed, or move along the ecliptic, from east to west, which 
produces an apparent movement of the stars round the ecliptic in an opposite direction. From the same 
cause the poles of our globe do not constantly point to the same part of the heavens, but describe circles 
round those points perpendicular to the plane or level of the earth's orbit, or the poles of the ecliptic, in a 
period of about twenty-six thousand years. Now, as the poles of the earth are inclined from the vertical to 
the orbit, or from the poles of the ecliptic, about 23|- degrees, the circles they apparently describe on the star- 





«. 


7 J -i^ 












V 


>^ — - — ^-^ 




^ 


»: / 










.X 


1 V 


-*• , 




,^^^.. % 


Viooo 




• 

•■ ... .• 


North 
Ecliptic Pole^ 






-^V^'o' 


t /■ 

A 9000. . 

/ .4000 B m: 


ARGO 


+ 




. .5000 


9000- 




/ 


> 


URA 


V 


8000^ <- 




South 
Ecliptic Pole 


RETkuLUM 


4000 
/ 




I 


.A. 


r 


9^ 

• 




L. \ 


^^5IP 


* present South P°^| 
— ^ of Heaven* S,^^ 




! 

5* 



Fia. G. Diagram showing Path traced out by the Earth's Axis owing to the Precession of the Equinoxes. 

sphere during each processional period, have each a diameter of 47 degrees, as represented in Figure G 
Accordingly the brightest star in the constellation of Ursa Minor — Polaris — has not always occupied its present 
position with respect to the North Pole of our globe. In the time of Hipparchus, for instance, the northern 
axis of the earth was directed to a point in the star-sphere distant from Polaris no less than ttvelve degrees, or 
twenty-four moon breadths. At present the distance between this star and the Pole is about one degree and a 
quarter, but 200 years hence, at the time of its nearest approach to the star, the distance will be less than 
one-half of a degree ; while 11,500 years hence the Pole will be pointing about 47 degrees from Polaris, and be 
directed only about 4| degrees from the star Vega in Lyra — by far the brightest star to which the North Pole 
is directed throughout the processional period of twenty-six thousand years. 

It is this gyratory movement of the earth which has produced so great an alteration in the positions of 
the constellations as viewed from different parts of the earth, thereby furnishing the means for arriving at the 
probable epoch when many of the figures were invented. The zodiacal constellations, for instance, were 
at the time of Hipparchus more than thirty degrees, or a whole sign, to the west of their present apparent 
positions. Since then, the crossing-points of the equator and the ecliptic, from which the positions of the 



14 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



I 



stars are determined,* have been carried along the ecliptic to that extent. This is why the twelve signs of 
the zodiac do not now coincide witli the constellations from which they received their names. Before Hip- 
parchus' time the zodiacal star-groups alone were used to mark off the various parts of the sun's yearly course ; 
but about his date astronomy was becoming a more exact science than hitherto, and a more accurate method 

ANCIENT AND MODERN POSITIONS OF STARS. 





150 


A.D. 




1890 


A.D. 




XAMB OF STAB. 


POSITIONS FROM OBSERVATIONS BY 


PTOLEMY. 


TRUE POSITIONS. 




SITUATED IN 

SIGN OF THE ZODIAC. 


LONGITUDE. 


LATITUDE 


SITUATED IN 

SIGN OF THE ZODIAC. 


LONGITUDE. 


LATITUDE. 


A Idebaran 




tl (Aries) 


12° 20' 


5° 10' S. 


2 (Taurus) 


8° 15' 


5° 29' S. 


Eigel . 




1 ,, 


20" 50' 


31° 30' S. 


2 „ 


15° 18' 


31° 9'S. 


Capella 




i 


25° 0' 


22° 30' N. 





20° 20' 


22° 52' N. 


Betelgeux 




2 (Taurus) 


2° 0' 


17' O'S. 





27° 13' 


16° 4' S. 


Sirius 




9 


17° 40' 


30° 10' S. 


3 (Gemini) 


12° 37' 


39° 32' S. 


Castor 




2 „ 


23° 20' 


9° 30' N. 


3 „ 


18° 43' 


10° 4'K 


Pollux 







26° 20' 


6° 15' N. 


3 „ 


21° 43' 


6° 40' N. 


Procyon 




^ it 


29° 30' 


16° 10' S. 


3 „ 


24° 19' 


15° 58' S. 


Regulus 




4 (Cancer) 


2° 30' 


0° lO'N. 


4 (Cancer) 


28" 19' 


0° 28' K. 


Spica 




5 (Leo) 


26° 20' 


2° 0' S. 


6 (ViRoa) 


22° 19' 


2° 2'S. 


A returns 




5 „ 


27° 0' 


31°30'K 


. 6 „ 


22° 42' 


30° 57' K 


A ntares 




7 (Libra) 


12° 20' 


4° O'S. 


8 .(Scorpio) 


8° 14' 


4° 33' S. 


Vega . 




8 (Scorpio) 


17° 20' 


62° O'N. 


9 (Sagittarius) 


13° 46' 


61° 46' N. 



was necessary for indicating the position of the sun in the ecliptic. Accordingly the ecliptic was divided into 
twelve exactly equal spaces or signs, and each sign into thirty spaces or degrees, each smaller division thus 
approximately marking the amount of apparent solar motion in a day. The first sign commenced with the 
vernal, or ascending equinox, the place occupied by the sun on the 20th of March when crossing the celestial 
equator in his journey northwards. At that time the constellation of the Ram occupied this position, so that 
the first sign was called Aries. In like manner the second, which Avas then occupied by the constellation of 
the Bull, received the name of Taurus, the third Cancer, &c.| The equinoctial points, however, as already 
mentioned, are not fixed, but, by the gyratory movement of the earth, carried completely round the ecliptic 
once every twenty-six thousand years, and the signs accordingly have moved away from the constellations from 

* The position of any heavenly body is determined by its angular distance north and south of the equator (called the 
declination), or by its distance north and south of the ecliptic or the sun's apparent anniTal jjath (called the latitude) ; and by its 
easterly distance from the vernal equinotical point measured on the equator (called the Right Ascension), or by its easterly distance 
from the same point measured on the ecliptic (called the longitude). Thus the position of a heavenly body with respect to the 
poles and the equator of the earth is determined by its declination and Right Ascension ; and its position with respect to the 
ecliptic by its latitude and longitude. 

t Each sign is equal to 30 degrees of longitude. 

% The signs are indicated as follows : — T Aries ; 8 Taurus ; n Gemini ; sb Cancer ; si Leo ; "e Virgo ; '^ Libra ; 
tri Scorpio ; i Sagittarius ; V? Capricornus ; xf Aquarius ; H Pisces. 



MOVEMENTti OF TBE EAIiTH WHICH AFFECT THE APPEARANCE OF THE HEAVENS. 15 



which they were designated at the beginning of our era, or tlie zodiacal star-groups have apparently 
travelled along the ecliptic to the ^vest of the places they then occupied. At present the constellation 
of Aries is in the sign of Taurus, the constellation of Taurus in the sign of Cancer, &c. The stars in other 
parts of the heavens have likewise apparently been displaced. Those, for example, to the north of the vernal 
equinox, are apparently being carried slantingly away from the equator, and those to the south caused to 
approach it, thus altering their declination as well as their right ascension. At the autumnal equinox exactly 
the opposite effect takes place; while near the solstices (see Plate 3) the stars appear simply to drift to the 
eastward in paths nearly parallel to the equator, their right ascensions only being altered. The stars are thus 
apparently carried round the poles of the ecliptic in paths exactly parallel to the earth's orbit. Therefore, 
while their longitudes, or distances from the "first point of Aries," measured on the ecliptic, are altered, their 
latitudes, or distances north or south of the ecliptic, always remain the same, as will be seen from the Table 
given on the opposite page. 

The effect produced by this apparent movement of the heavens, owing to the precessional motion of the 
earth, is somewhat striking. In an interval of about thirteen thousand years, or one-half of the precessional 
period, the constellations apparently occupy diametrically opposite positions on the star-sphere. Those groups 
which, thirteen thousand years ago, were seen during the winter months, are now visible only during the 
summer ; and many of the constellations which then appeared when on the meridian low down on the 
horizon, are at present situated in the sky at considerable altitudes (see Plate 3), 

NUTATION. 

While, however, the poles of the earth, as in the precessional movement, gyrate round a vertical to the 
orbit, they do not, as might be supposed, move in uniform circles, as 
represented in Figure 6. Owing to the continual variation of the com- 
bination of the forces of the sun and moon exerted on the spheroidal 
figure of the earth, the inclLnation of the axis varies slightly, as well 
as the velocity of its movement in the precessional circle. This causes 
the poles of our globe, in swaying round the poles of the ecliptic, to 
trace on the star sphere a wavy circle, as indicated in Fig. 7. In this 
movement the poles sway on either side of the circle A B to the extent 
of about nine seconds of arc, or by about the eighteen-thousandth part 
of the diameter of the precessional circle A B. Each wave occupies 
about 18§ years, equal to a complete revolution of the nodes, or crossing 
points, of the lunar orbit and the ecliptic plane ; so that in each 
precessional period of twenty -six thousand years, no less than 1400 



tOUPTIC POLE 
OR POINT PERPEN0ICUL4R 

TO THE EARTHS 
OHsn 



waves are described by the poles of our globe. Like the precessional j?j(. 7 diagram showing path traced out 
movement already mentioned, only the right ascensions, declinations, gy the poles owing to nutation. 
and longitudes of stars are affected by nutation ; the latitudes remain- 
ing constant. This minute, wavy movement of the poles was discovered in the year 1728 by the telescopic 
researches of the astronomer Bradley, but its cause was not fully explained till the year 1747. 

aberration. 

But the stars are subjected to still another apparent displacement, — one produced by the rapid motion 
of the earth in her orbit, combined with the sensible movement of light travelling to us from the stars. 
Our globe journeys yearly round the sun in a nearly circular path whose length is about 580 millions 
of miles, so that each second she travels over a space equal to about nineteen miles. Light, on the other 
hand, travels at the inconceivable velocity of about 18G thousand miles per second. Now, when the earth 
moves perpendicularly to the direction of a star, as at A, Fig. 8, the star will not appear as at S\ but, 



16 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



owing to the earth's movement across the falling light-rays, in the direction of S^ — i.e., the star is apparently 
thrown out of its true position in the heavens, in the same direction as that in which the earth moves; 
and the amount of displacement depends entirely on the proportion between the velocities of our globe and 
that of light. The same effect is produced when one walks in a shower of rain. If the drops fall per- 
pendicularly, they will only appear to do so if the observer remain stationary, for whenever he moves the 
drops will appear to fall slantingly towards him, and the quicker his motion the greater the apparent 
inclination of the falling rain-drops. In the case of the light from the stars, the angular displacement, or 
the angle S^ A S^, is about twenty seconds of arc — a very minute quantity indeed, yet one easily perceptible 

to modern astronomical instruments. 

Of course the displacement is greatest when the earth is in the position 
of A, with respect to a star, or moving nearly at right angles to the light- 
rays travelling from the star, which it does for each star at intervals of six 
months, or one-half of a revolution of her orbit. Three months before and 
after the earth moves perpendicularly to the star's light-rays, when travel- 
ling to or from the star, as at C and D, the aberration is at zero, and if 
the star be situated nearly on the same plane as the orbit of our globe, 
there will be no displacement whatever, while stars above and below the 
ecliptic level will be slightly displaced in a vertical direction. Thus through- 
out the year, each star, by the rapid moving of the earth, is caused appar- 
ently to describe a minute elliptical curve in the heavens, whose greater 
axis is 41", or twice 20"'5 in length, and lies parallel to the ecliptic ; while 
the smaller axis lies perpendicular to the orbit, and increases in dimensions 
as the ecliptic poles are approached. 

The displacement through aberration, which at first was thought to 
be the effect of parallax, was discovered by Hooke in the year 1669 
from observations of the star 7 in the constellation of Draco, a star which passes very near the zenith of 
London. It was not truly accounted for, however, till 1726, when Bradley, who was then thinking over 
the cause of the displacement, was accidentally led to the solution of the problem. One day, he happened to 
be crossing the Thames in a small boat, and by the strength of the current was unable to reach 
a certain part of the opposite bank at which he desired to land. Noticing that the amount of angular 
displacement in the water by the flowing stream depended on the velocities of the boat and the current, 
he was led to the true explanation of aberration — viz., the result of the combined velocities of the 
earth and light. 




Fig. 8. diagram explaining aberra- 
tion OF LIGHT. 



MOVEMENTS OF THE EARTH WHICH AFFECT THE APPEARANCE OF THE HEAVENS. 



17 



Proper Motion. 




U, CASSIOPEIAE 



'APPARENT 
loiAMETER 
OFMOON 



1200,1100,1000,900 SOO 700 600 500 400 30O 200 100 
SCALE OF MINUTES OF ARC 



The different apparent movements to which every heavenly body is subjected from the real moving 

of the earth, are, therefore, the Diurnal, Annual, and Precessional 
rotations, and the Nutational and Aberrational displacements 
— all of which occur in regular periods. There are, however, 
other displacements which affect each star differently both 
in amount and direction. These, unlike the others above 
mentioned, are real, and are produced by the actual moving 
of the stars through space. They are called " proper motions " 
of the stars, and were first noticed by Halley in the year 
1718. The stars are no longer considered as being fixed, 
for each is now known to be constantly changing its place in 
the heavens. The brilliant star Arcturus, for instance, has, 
since the beginning of our era, moved over a space on the 
star-sphere equal to two and a-half times the apparent diameter 
of the moon ; while the well-known small star 61, in the con- 
stellation of Cygnus, moves so rapidly that m less than 300,000 years it will travel completely round the 
heavens. Fig. 9 indicates the comparative apparent angular displacements of several stars with large 
proper motions in ten thousand years' time. 

The effect of this real movement of the stars is, after long intervals, to completely alter the appear- 



FlG. 9. RELATIVE PROPORTION OF PROPER 
MOTION OP STARS. 



CASSIOPEIA 

<-• 

■••, • «• 

cC-0'' 
Present 


ORIONx 
•*• 

ap 

Present 


THE PLOUGH 

• ^ ^■■■■■■■■■■■■' 
....■■■■■■ • "f >A 

•■■^ w 

Present 


<-• 

— <iy 

MIO.UOO Yeais hence • l 


■ \ f 

100,000* Years hence 


......rt» 

<».,. . .■-■■■■■■ 

■. ^* r-- j,M' 

7* . ^m 

100,000 Vears hence 



Fig. 10. Alterations in Appearance op some of the Constellations 100,000 years hence, owing to 

"Proper Motion." 



ance of the heavens, and to destroy the forms of many well-known constellation figures. Fig. 10 
represents different views of three important groups after an interval of 100,000 years. 

In the proper motion, however, we do not see all of a star's movement through space. A star 
may appear fixed in the heavens, and yet it may be travelling to or from the eartli or in the tlirection 
of the line of sight. If, then, this latter quantity be known, along with its distance, and the amount 



18 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



of proper, or apparent lateral, motion in the heavens, the velocity of the star's true movement in space 
can easily be computed. Thus, in Fig. 11, if A B represents the proper motion of 
a star, B C its movement in the line of sight, in this case towards the earth, A C 
will then be its true movement in space. Now, by means of the spectroscope, 
the velocity in the line B C can be determined ; so that, knowing the distance of 
the star from our system, or E A, the actual velocity of the star in its journey 
through space, or A C, can be calculated. In many cases these velocities are very 
great indeed, being often as much as one hundred miles per second. Therefore, 
many of the stars, though apparently fixed in the sky, are in reality rushing through 
space at a velocity of over four times that of our earth in her orbital revolution, and 
two hundred times greater than the speed of a projectile from a rifled cannon. 




Fig. 11. DIAGRAM 
SHOWING HOW THE 
ACTUAL VELOCITY 
OF STARS IS CALCU- 
LATED. 



TABLE OF ACTUAL VELOCITY OF STARS. 



a Centauri has a probable minimum velocity of 


27 


miles 


per 


second. 


Capella 


!) >J J) )) . . r . . 


30 


)) 




;) 


Sirius 


>) )) n )) ...... 


32 


)) 




)> 


61 Cygxi 


5) )i ;t 11 - * . , . 


40 


M 




)) 


Vega 


)) )5 ;5 )' ' . T . 


50 


)) 




J> 


s Indi 


)) )) !l? )) ..... 


65 


)) 




)) 


Arcturiis 


)) )) 5) )) = . . . . 


70 


J) 




?j 


No. 1830 


of Groombridge Catalogue (a small star in Ursa Major), 










has 


a probable minimum velocity of . . . . 


200 


)) 




)) 



E- 

<: 

1 

< 

X 

o 

.J 
CO 



< 

CO 
X 




m 

X 

& 

M 

X 
z 

E- 
D 

o 

CO 



Q 
CO 

z 

s 

E- 

cc 




CHAPTER III. 



THE SIDEREAL HEAVENS. 



"Eoll on, ye stars! exult in youthful prime, 
Mark with bright curves the printless steps of time ; 
Near and more near your beamy cars approach. 
And lessening orbs on lessening orbs encroach." — Erasmus Darwin. 



THE DISTANCES OF THE STARS. 

That the stars are situated at great distances from our system is well known ; but few, even for a moment, 

imagine how enormous those distances in reality are. Previous to 
the year 1838, astronomers even were uncertain as to the immensity 
of the spaces lying between us and many of the orbs composing the 
sidereal universe. In that year, the astronomer Bessel, from numerous 
delicate observations of the small star 61 of Cygnus, was enabled to 
announce that he had determined the distance of that orb ; and had 
discovered somethinof of the n)aonitude of the scale on which the 
great starry system was built. A short time afterwards, the distance 
of another star was determined. Henderson, from observations made 
in the Southern Hemisphere, found that the bright star a Centauri 
was situated from us at a distance of about half that of 61 Cygni, 
or about eighteen billions of miles. Since then the distances of 
quite a number of stars in both hemispheres have been very fairly 
determined ; but in every case it has been found that these orbs are 
removed much further from us than « Centauri, which, therefore, 
still remains the nearest known star to our system. 

The problem of determining the distances of the stai-s is one of the 

most difficult that the astronomer has to solve. It requires the highest 

observational skill that the human intellect is at present capable of, 

combined with the most accurate instruments that it is possible for 

human hands to make ; and in the great majority of cases, the distances 

of those orbs are so enormous that it is impossible to discover 

them. In attempting the solution of this grand problem — viz., to apply 

the sounding line to the depths of space, the astronomer employs the 

same method as a surveyor when measuring the distance of some 

inaccessible object. A base line at right angles to the object is carefully measured, and from each end of it 

the angle between the object and the opposite end of the base line is determined, from which data, by 

means of the properties of triangles, the distance of the object can be calculated 




Fig. 12. DIAGRAM SHOWING HOW THE 
DISTANCE OF STARS IS MEASURED. 



In determining the 



1!) 



20 A POPULAR HANDBOOK AND ATLAS OP ASTRONOMY. 



moon's distance, a chord of the terrestrial surface can successfully be employed as a base line. The distance 
of the sun, however, is so great that even the whole diameter of our globe, or 7918 miles, is a base line 
too insignificant to measure it ; while the stars are so far away that a base line even a hundred times 
longer would still be perfectly useless. Fortunately for astronomical science, a longer base line than this 
can be had, for in attempting the measurement of a star's distance, the astronomer employs one whose length 
is twenty-three thousand times greater than the diameter of the earth, for he employs the whole diameter 
of the orbit of our globe, a length of over 185 millions of miles. From one end of this enormous base 
line, the observer from the earth at A (Figure 12), carefully measures the angular distance of the star 
S, from some small and more distant star, as M, or he determines the very minute angle CAM Six 
months afterwards, when our globe has completed one-half of her annual revolution, and has carried the 
observer to the other end of his base line, at B, the star S will no longer appear at C, as when viewed from 
A, but at D, from the parallactic displacement of the star, brought about by the change of the observer's 
position. The astronomer, therefore, from his new position at B, determines the new angle M B D, and 
from these angles he can get the angle AS B, or the annual parallax of S, from which he can calculate 
the distance of the star. 

It will be noticed from Fig. 12 that the further S is from A and B, or the more distant a star is 
from the earth, the smaller becomes its apparent angular displacement or its annual parallax. In the case of 
the nearest star, this minute angle is less than one second of arc, or about the same angle as that under which 
one quarter of an inch would appear as viewed from a distance of a mile ; for the nearest star is no less than 
275 thousand times more distant than the sun ! This distance is so great, that an object, travelling 
continuously at the velocity of an express train, would only journey over it in about sixty millions of years, 
Even light, which in each second travels over a space of 186 thousand miles — thus reaching us from the 
moon in about one second and a-quarter, and from the sun in seven and a-half minutes — actually requires 
four years to reach our earth from a Centauri. Such is the distance of the nearest star ! The star next 
in point of distance, or the small star 61 of Cygnus, is situated at- a distance of over 469 thousand times 
greater than that of the sun, and thus its light in journeying to us requires seven years. From the brilliant 
star Sirius light occupies ten years in travelling; from Aldeharan, fourteen years; from Vega, twenty-two 
years ; and from Polaris, no less than thirty-six years. 

These, however, are stars that lie nearest to our system. The vast majority of those seen with the 
unaided eye are situated at distances considerably greater than these. So vast are their distances in most 
cases, that no parallactic displacement can be detected, even with the most accurate and powerful instruments, 
viewed from opposite ends of that great base line, the diameter of the earth's orbit. Such are the distances 
of the stars visible to the naked eye. The millions of faint stars rendered visible by the telescope are 
undoubtedly more distant still ; so that, in many instances, their light has occupied hundreds and thousands 
of years in traversing that mighty abyss which lies between them and our earth. 

We do not, therefore, see the heavenly bodies in the positions they occupy, or in the conditions in which 
they exist, at present, but at the time when their light-rays, which now enter our eyes, first set out on their 
journey to our system. When we look at the moon, for instance, we see her as she existed one second ago ; 
the sun, seven and a-half minutes ago ; a Centauri, four years ago ; and the other stars, tens, hundreds, and 
in many cases, thousands of years from the present time. The astronomer, then, when analysing the light of a 
star, does not thereby determine its present condition, but its condition some time in the distant past — 
hundreds of years, it may be, before the instrument he employs was known to the human race. Such, then, 
are the distances of the stars, which reveal to us the immensity of the depths of those parts of space that lie 
nearest to our system, and those still greater depths which lie beyond — depths which to us will probably ever 
remain unfathomable. 



THE SIDEREAL HEAVENS. 



21 



THE DISTANCES OF THE NEAEER STARS. 



NAME OF STAR. 


ANNUAL PARALLAX. 


Number of times 

more distant from the Eartk 

than the Sun. 


DISTANCE. 


Years occupied l)y light 

in travelling from the star 

to the Earth. 


a Centauri 






0'75 seconds of arc. 


275,000 


251 


BILLIONS of miles 


4-3 years. 


61 Cygni. 






0-44 „ 


469,000 


43i 


» >> 


7-4 „ 


Sirius. 






0-33 „ 


625,000 


58 


)j )> 


9-9 „ 


Procyon 






0-27 „ 


761,000 


701 


)> )) 


120 „ 


a Draconis 






0-25 „ 


838,000 


78 


)> ji 


13-2 „ 


Aldeharan 






0-24 „ 


874,000 


81 


>) )) 


13-8 „ 


i Indi . 






0-22 „ 


937,000 


87 


)) ?> 


14-4 „ 


Altair. 






0-19 „ 


1,086,000 


103 


J) >; 


17-1 „ 


n Cassiopeij-; 






0-16 „ 


1,272,000 


118 


!> )) 


20-1 „ 


Vega . 






0-15 „ 


1,373,000 


127 


»> )) 


21-7 „ 


Capella 






0-11 „ 


1,875,000 


174 


>) )> 


29-6 „ 


Arcturus 






0-094 „ 


2,194,000 


203 


)) )J 


34-7 „ 


Polaris 






0-089 „ 


2,318,000 


215 


J) 1) 


36 


IX, CASSIOPEIiE . 






0-060 „ 


3,438,000 


319 


)» )> 


54 


No. 1830 Groom- ^ 
bridge Catalogue ( 


0045 „ 


4,583,000 


425 


>J )5 


72 



THE NATURE OF THE STARS. 

The distances at which the stars are situated reveal to us something of their nature. When our earth 
was considered to be the centre of the universe, and before the telescope had been directed to the heavens, the 
stars were thought to be comparatively near, and were in consequence believed to be simply small lights 
suspended in the sky. When, however, the Copernican theory was established, the stars were proved to be 
very distant orbs indeed. Viewed from each end of the earth's orbit no large displacement could be detected, 
which proved the immensity of their distances. In fact, one of the chief arguments against the belief in 
the orbital movement of our globe, was the acceptance of the immensity of the stellar distances, and the 
gigantic sizes of the stars as a direct consequence. The earth, however, is now known to revolve ; in several 
instances the distances of the stars have been determined ; and from those distances it is also known that the 
stars are orbs, thousands of times larger than our globe, and in most cases gigantic even as our sun. Being 
self-luminous they were indeed looked upon as globes in every respect identical with the great centre of 
the solar system. They were believed to be gigantic, fiery, gaseous masses, in which there were ever taking 
place, as on our sun, the most tremendous disturbances. This with certainty is now known to be the case. 
That truly marvellous instrument, the spectroscope, when applied to the study of the heavens, at once revealed 
the fact that each star is really a sun. Being so distant, it of course appears very insignificant ; but, if viewed 
from the same comparative nearness as we view our sun, it would in many instances appear several times 
larger and hotter than the solar orb. Our sun is thus simply an enlarged view of every one of the millions of 
stars revealed by means of the telescope ; and each star, on the other hand, is a diminished view of our own 
gigantic sun, 



22 



A POPULAB HANDBOOK AND ATLAS OF ASTRONOMY. 



As mentioned in a former chapter, these suns are constantly moving through the depths of space at 
velocities hundi'eds of times greater than the speed of a projectile — resembling, in fact, so many gigantic balb 
fired from some mighty piece of ordnance. Being suns, they are, therefore, centres of planetary systems ; so 
that each orb in its majestic sweep through the infinite void, carries along with it its system of revolving 
worlds. Like his companions, our sun is also rapidly tra<velling through space. At pl-esent, his orbital velocity 
is thought to be about fifteen miles per second, whixjh is considerably less than many of his fellow suns. That 
part of the heavens towards which he is travelling is situated on the confines of the constellation of Hercules, 
near the brilliant star Vega — a point on the star-sphere diametrically opposite the place towards which tho 
brightest star in the heavens, the star Sirius, is apparently moving. 




DIFFERENT ORDERS OF STARS. 

The spectroscope, however, not only proves that the stars are suns, but that, like the various planets, they 
are arranged into classes. Sirius, for instance, is found to belong to a type of star totally different in appear- 
ance from our sun. As seen in Plate 19, its spectrum is quite different from the solar spectrum. The chief 
characteristic in the spectrum of Sirius is the existence of several exceedingly broad, dark bands. These, as is 
now known, are produced by a dense layer of hydrogen gas surrounding the star, or forming part of its fiery 

atmosphere. The density of the gas, as witnessed in the breadth 
of the dark lines in the spectrum, is entirely owing to the great 
attraction exerted on it by the globe of the star — an attraction 
much greater than that exerted by our sun on the same gas 
forming part of his atmosphere. Thus, Sirius is a globe much 
more massive, or heavy, than the solar orb. But the mass of 
Sirius is known in another way. In the year 1862, a faint com- 
panion star was accidentally discovered revolving round Sirius. 
From the period of its revolution, combined with its distance, tho 
mass of the larger star was determined. The two globes, distant 
though they be, can, as it were, be placed in the astronomer's 
scales, and compared with our sun ; for the attraction of any two 
orbs, and the velocities of their revolutions, entirely depend on 
their weights or masses. From the fact, then, that the companion 
to Sii'ius completes its revolution in so short a period as forty-nine years, while its distance from him is 
greater than that of the planet Neptune from our central orb, Sirius is known to be about twenty-six times, 
and the companion about nine times, heavier than the sun. 

But Sirius is not only very much heavier than our sun ; he is also considerably larger. As 
already mentioned, he is the brightest star in the heavens, and being situated from us at a distance of over 
625 thousand times that of the sun, it proves that in surface Sii'ius vastly exceeds our central orb. In 
fact, from his enormous distance and great brilliancy, Sirius is believed to exceed our sun in volume at least 
500 times (see Fig. 13). 

Sirius, then, belongs to a type of suns of a much higher order than our own. The stars of this class are, 
like Sirius, readily distinguished by their clear, bluish light. The class contains most of the brighter stars 
such as Vega, Rigel, Procyon, Capella, &c. The stars belonging to the second class, on the other hand, are of 
a yellowish colour, and have spectra much the same as the solar spectrum (see Plate 19). Now, as the 
hydrogen bands in the spectra of the stars of this type are not very conspicuous, and as the intensity of the 
light is not great, these suns are doubtless inferior in volume and mass to the members of the first type. In 
fact, between the members of these classes, there will be at least as marked a difference in dimensions as 



Fig. 13. 



COMPARATIVE SIZES OF THE SUN AND SIRIUS. 



I 



THE SIDEREAL HEAVENS. 



23 



there is between the sun and Sirius. Thus, our sun belongs to an inferior order of suns, of which Altair, 
Ardurus, Aldebaran, &c., are members. 

But the spectroscope has revealed the existence of a third class of stars {see Plate 19). Strangely 
enough the spectrum of the stars of this type is similar in appearance to the spectrum of a sun-spot, from 
which one would suppose that the stars of this class (to which a Herculis belongs) will have their surfaces 
greatly covered with sun-spots. Now, the spots on the solar surface are subject to a variation in number 
throughout a fairly regular period. Once in about every eleven years, for instance, the number of spots on the 
sun's surface, or the amount of solar disturbance of which the spots are indices, reaches its maximum ; and 
midway between the epochs of maxima, very few spots are formed. Those stars, then, that have spectra like 
sun-spots will also probably have at one time many more spots on their surfaces than at another time. In 
short, each of the stars of this class will, like our sun, but in a more marked degree, have their maximum and 
minimum number of spots. Thus, one would suppose, these stars will not always shine with the same degree 



TABLE OF CLASSES OF STARS. 



FIRST CLASS. 


Stars of a bluish-white colour. 






Sirius. 




Fomalhaut. 


j8, 7, £, 7\ Canis MAJor.is. 


a, S, y, d Persei. 


Vega. 




Regulus. 


b, i, ^ Orionis. 


'-/., y, X OpHIUCHI. 


Rigel. 




Castor. 


a, y, Z, Pegasi. 


a, /3, y CORONiE BOK 


Procyon, 




Thuban. 


/3, 7, S, I, ^, n Urs^ Majoris. 


a PlSCIUM. 


Spica. 






jS, d, I Cassiopeia. 


/3, d, Z„ ri Leonis. 


SECOND CLASS 


Yellowish Stars like the Sun. 






Altair. 




Arcturus. 


a. ^, Yj Cassiopele. 


/3, 7» 1) ^> '> ?> Z Dracoxis. 


Capella. 




«,^,7>^^r'-CYGNi. 


a, 5 Serpentis. 


/S, ^, J), T Herculis. 


Pollux. 




a IjRSiE MaJORIS. 


|S, 6, £, n, g BooTis. 


7, £, /x Leonis. 


Aldebaran. 




a\ or CaPRICORNI. 


/3, y, r, n Cephei. 


/3, i A'iRGINIS. 


THIRD CLASS. 


Red and Orange Stars. 






Antares. 




Alphard. 


jS, f Pegasi. 


5 and o^ Orionis. 


Betelgeux. 




a Herculis. 


d, a ViRGINlS. 


f, a Persei. 


Mira. 




[I Cephei. 


?r, V AuRlGiE. 


119 Tauri. 



of brilliancy, as an increase of spots would certainly somewhat diminish the quantity of light radiated from 
their surfaces. This, indeed, is found actually to be the case with the majority of the stars belonging to this, 
the third type. In fact, these stars are for the most part what are known as Variable Stars— i.e., stars whose 
brilliancy is subject to more or less variation throughout both regular and irregular periods. 

The stars of this third class are generally of a reddish colour, thus, probably, denoting a further and cooler 
stage than the yellow stars— the class to which our sun belongs. These three orders of suns above-mentioned 
are the principal types into which the stars in our sidereal universe are divided, as at present known. A fourth 
class has recently been revealed, but the stars belonging to it are not very brilliant, and are evidently suns 
considerably smaller than our own. Very probably there are numerous other classes yet to be discovered 
Enough, however, has already been revealed to show clearly that the stars are not all built on one plan, as was 
once supposed, but that, as in the solar system, there are ditferent orders of planets, so in the immensity of 
star-strewn space, there are various orders of suns ; that among the stars, as everywhere in Nature, there is. 
along with a wonderful unity, the greatest variety — in size, condition, light, heat, colour, and movement ; and 
that, indeed, " one star diffcreth from another star m glory." 



24 A POPULAR SANBBOOK AND ATLAS OF ASTRONOMY. 



DOUBLE STARS. 

In the year 1664 the astronomer Hooke, while observing a comet, accidentally viewed the star 7 in the 
constellation of Aries, and was surprised to find that it was unlike many others he had seen, in respect of its 
being composed of two stars. In this manner was the first double star discovered. Since that time, with each 
improvement of the telescope, large numbers of others have been found, till at present no less than upwards of 
ten thousand are known, and this number is steadily being added to every year. In most cases the angular 
distances between the components do not exceed thirty seconds of arc, being often as close as one quarter of a 
second. The closer ones require, of course, the most powerful instruments to render them visible, because the 
greater number of telescopes do not separate double stars which are closer than one second. Recently, by 
means of the spectroscope, several double stars that are closer than even the most powerful telescope will 
divide, have been discovered; as from its revolution the changing position of the small star produces a regular 
widening of the dark lines of the spectrum. In Plate 5 there are given telescopic views of the more remark- 
able of these objects, and the positions of many hundreds of them are indicated in the accompanying twelve 
large Charts of the Heavens. 

The double stars are in general beautifully coloured. In the case of those whose components are 
nearly equal in magnitude there is no contrast of colour whatever. In the case of those, however, where the 
companion greatly differs from the larger one in size, the colours distinctly differ, and perfectly blend. The 
colours of the components are, in fact, what is known as complementary, for the colour of the small star 
lies further up, or nearer the violet end of the spectrum, than the colour of the large one. If the larger star, 
for example, is of an orange colour, the smaller one is then of a bluish tint ; and if red in colour, the companion 
is green. Seeing that this peculiarity exists, one might suppose that the components of a double star would 
in some way be connected. Such, indeed, in many instances, is really the case ; for the two suns are found to 
have movements which are produced by each other's attraction. In Plate 5 there are represented the orbits of 
four of the more remarkable of these binary stars, as they have been designated — viz., of a Centauri, of T 
Herculis, of 7 ViRGiNis, and of q Urs^ Majoris. The periods in which the companions complete their 
orbital revolutions depend, of course, on the weights, or masses, of the larger stars, and the distances between 
the components, and are thus likely to have a considerable range. The shortest known period of revolution of 
a binary star, as in the case of § Equulei, is one of fourteen years ; while the longest, as in X, Aquarii, is 
about 1600 years. 

But not only are two stars physically connected ; three and often more stars sometimes form one system. 
One of the most remarkable of the multiple systems is e Lyr^, a small star near the bright star Vega. With 
a very small telescope this object appears as a well separated double star. In larger instruments, however, 
each of the components is again divided into two stars, so that it is in reality a double binary system {see 
Plate 5). Another remarkable system is the triple one of <, Cancri ; the members of which perform rather 
curious movements. The two large stars revolve round their common centre of gravity after the ordinary 
manner of binary stars, in a period of about sixty years ; while the third, and smallest star, moves slowly 
round the two large orbs in a much longer period — one probably of several hundred years in extent. 

In other instances the components of multiple systems are not arranged into pairs, but are situated from 
each other, as in the case of the star Q Orionis, at nearly equal distances. This, from the constantly altering 
attractive forces of the different members of the group on one another, will produce more wonderful movements 
even than those above-mentioned. These cases, however, are not very numerous. In general a large star is 
seen with several tiny companions, an arrangement more of the nature of a large sun and smaller ones, or 
planets, revolving round it. These apparently tiny companions, requiring the largest telescopes to render 
them visible, are not by any means insignificant. If, for instance, a planet as gigantic as Jupiter revolved 
round the nearest star, it would be invisible to the most powerful instrument. This proves that the small 



I 



DOUBLE Stars— Plate 5. 



M.gn,t.,de. TELESCOPIC APPEARANCES 

•••utff..?^.^--^A»v-OF THE MORE INTERESTING DOUBLE STARS 



Stale 




ORBITS OF BINARY STARS 



^ Herculis 

(Period 35 year! 




/ > VlROINIS 
'(Period I70>ears)y 



THE SIDEREAL HEAVENS. 



25 



companions seen surrounding those stars, which, like Vega, are knowu to be many times more distant than 
a Centauri, are undoubtedly hundreds of times larger than the giant planet of our system. In fact, as already 
mentioned, one of these faint companions, the satellite of Sirius, is even more massive and gigantic than 
our sun. 



TABLE OF BINARY STARS. 



NAME OF STAR. 


MAGNITUDES 
OF COMPONENTS. 


PERIOD 
OF REVOLUTION. 


NAME OF STAR. 


MAGNITUDES 
OF COMPONENTS. 


PERIOD 

OF imrOLUTION. 


fi Eqoulei . 


4-5 and 5 


14 years 


g BoOTIS . 


4-5 and 6-5 


127-4 years 


42 Comae Ber. . 


6 „ 6 


25-7 „ 


4 Aquarii , 


6 » 7 


129-8 „ 


8 Sextantis 


5-5 „ 6-5 


33 „ 


7 ViRGINIS . 


3 „ 3-2 


185 




^ Herculis 


3 „ 5-5 


34 4 „ 


o" Eridani . 


9-5 „ 10-5 


200 




T] CoRONAE Bob. . 


5-5 „ 6 


41-6 „ 


r OpHIUCUI 


5 „ 6 


218 




Sirius 


1 „ 9 


49 „ 


n CassiopeivE 


4 „ 7-3 


195-2 




y CoRONAE AUST. 


5-5 „ 5-5 


55 „ 


44 Boons . 


5-3 „ 6 


261 




^ Canceri (triple) 


(A. 5-5 
\ B. 6-2 
(C. 6-6 


60 „ 
600 „ 


,a" BoOTIS . 

d Cygni 


6-5 „ 8 
3 „ 8 


280 
336 




t, Urs^ Majoris 


4 and 5 


60-8 „ 


36 Andromedae . 


6 „ 7 


349 




a Centauri 


1 „ 2 


77-4 „ 


7 Leonis . 


2 „ 3-5 


407 




70 Ophiuchi 


4-5 „ 6 


94-4 „ 


/x Draconis 


5 „ 5 


562 




7 CoRONAE BOR. . 


4 „ 6 


95-5 „ 


12 Lyncis . 


6 „ 6-5 


676 




^ SCORPII . 


5 „ 5-2 


9G „ 


a Coronae Bor. . 


5.5 „ 6-5 


846 




tu Leonis . 


6 „ 7 


111 „ 


Castor 


2-5 „ 2-8 


997 




25 Canum Venat. 


6 „ 7 


124 „ 


^ Aquarii . 


4 „ 5-5 


1600 





VARIABLE STARS. 

When the stars are closely examined from time to time, it is found that a number of them alter in 
brilliancy. In fact, every star in the heavens must slowly or otherwise be changing in brightness ; for 
it cannot be supposed that a fiery gaseous mass, such as a star, can long remain in the same condition 
as to temperature, and consequently as to the amount and intensity of its light. Within historic times 
there are several instances where stars have either diminished in brightness, or their surrounding 
companions have increased. If during only the last few hundred years accurate determination of the 
relative brilliancy of the stars had been made, as is done now, the known number of cases of gradual 
variation would doubtless be very great indeed ; as all the stars are growing older, and must ultimately 
become dark orbs. These stars, however, whose light is thus subject to a gradual diminution, are not 
what are properly known as variable stars. Variable stars are those whose lustre passes from a maximum 
to a minimum in periods that are either regular or irregular. 

Like the ordinary stars, those that are variable can be arranged into classes. The brilliancy of those 
that belong to the first class fluctuates in a very regular period. This class is what is known as the 
" Algol type," from the star Algol, in the constellation of Perseus, the first star of this class discovered. 



26 



A POPTJLAE HANDBOOK AND ATLAS OF ASTBONOMY. 



Algol, in general, shines as a second magnitude star ; once every sixty-nine hours, however, it slowly 
decreases in brightness, till in about four and a-half hours it has lost about five-sixths of its light, and 
appears as a star of the fourth magnitude. It now shines as such for about nineteen minutes, and then 
in three and a-half hours' time regains its maximum brightness, and retains it for the remaining part 
of its short period. These regular variations to which the light of the stars of the "Algol type" are 
subject can only be produced by large, dark planets revolving round them, as the spectrum remains 
unaltered throughout the entire period of revolution, being only diminished in brightness. Each time, 
for instance, the dark companion to one of these stars passes exactly between us and the star, a partial 
eclipse takes place ; a considerable quantity of light is thus intercepted ; and the star shines with 
greatly diminished brightness. In fact, from the known distance of the star, and the amount and 
variation of its light, it is possible to determine the approximate size of the star and its companion. 

In the case of Algol it is thought that the star itself is a sun whose 
diameter is about one million of miles ; while the companion is a globe 
about the same size as our sun. 

The variations of lustre of the next class of stars are performed in 
exactly the opposite manner to those of the Algol type. Instead of shining 
for the most part at the maximum brilliancy, and decreasing in magnitude 
only for short intervals, the stars of this class shine generally at the 
minhnum lustre, and increase their light at fairly regular intervals. The 
first star belonging to this type was discovered in the year 1596. It is 
a star situated in the constellation of Cetus, called Mira — the wonderful. 
Usually this remarkable star is invisible to the unaided eye, and appears 
as faint as a star of the tenth magnitude. It becomes visible, however, 
once every eleven months, and increases in brightness until it sometimes 
appears as conspicuous as a second magnitude star. This maximum bril- 
liancy is retained for but little over a week, when, more slowly than at 
its increase, the star again gradually becomes invisible. These variations 
from minimum to maximum, and then back to minimum again, occupy 
about three months ; so that for about eight months at a time the star cannot be seen without the aid 
of a telescope. 

The third type of stars is well represented by the star /3 Lyrae. In this case the variations take place 
somewhat regularly, but in each period two, and sometimes more, maxima and minima occur. 

The stars of the fourth group perform their variations in a manner that is totally different from any of the 
above-mentioned tjrpes. Like the members of these classes, the stars of the fourth type often have a great 
range of variation; but, unlike those stars, the variations of the last-mentioned group are performed in irregular 
periods. The principal star of this class is situated in the southern hemisphere in the constellation of Argo, 
the star rj, certainly the most remarkable variable star in the heavens. In this star the range of magnitude is 
probably more extensive than in any other. Sometimes it is so conspicuous that it rivals even Sirius, the 
brightest of all stars, while at other times it is invisible to the naked eye ; thus radiating at maximum, no less 
than twenty-five thousand times more light than at minimum. These variations of lustre do not, as indicated 
by Figure 14, occur regularly, and the increase or decrease of brilliancy is not uniform, or continuous. 
iStrangely enough this remarkable star is surrounded- by a nebula, which in some way appears to be connected 
with the star; as its misty light is also subject to variation. 

There is yet another class of stars which may be mentioned — a class that at first sight does not seem to 
be in any way connected with the variable stars. This type, however, may simply be a different stage of the 
Mira class — i.e., stars which do not in general appear conspicuous, and only occasionally increase their light. 




Fig. 14. CURVES showing varia 

TION OF MAGNITUDE OF DIF 
FERENT CLASSES OF STARS. 



The Pleiades — Plate 




TABLE OF THE MORE INTERESTING VARIABLE STARS. 



First 


Class. 


Second 


Class. 




RANGE OF 






RANGE OF 




NAME OF STAR. 


VARIATION OF 
MAGNITUDE. 


PERIOD. 


NAME OF STAR. 


VARIATION OF 
MAGNITUDE. 


PERIOD. 


/3 Pbrsei (Algol), . 


2-3 to 


3-5 


2 d. 20 h. 49 m. 55 s. 


Ceti (Miru), 


1-7 to 9-5 


331-3 days. 


X Tauri, 


3-4 „ 


4-2 


3d. 22 h. 52m. 12s. 


T Monocerotis, . 


6 , 


, 7-6 


27 days. 


S MONOCEROTIS, . 


4-9 „ 


5-4 


3d, 9 h. 36 m. 


E Leonis, 


5 , 


, 10 


313 days. 


E Canis Majoris, 


5-9 „ 


6-7 


Id. 3h. 15 ra. 55s. 


E Hydrae, . 


3-5 , 


, 10 


497 days. 


8 Librae, . 


5 „ 


6-2 


2d. 7 h. 51 m. 23 s. 


E Coronae, . 


6 , 


, 12 


376 day.s. 


U Ophiuchi, 


6 „ 


6-7 


Od. 20L 7m. 42s. 


y^ Cygni, 


4-5 , 


, 13 


406 days. 


Y Sagittarii, 


6-2 „ 


7-4 


2d. lOh. 5m. 


E Aquarii, . 


5-8 , 


, 11 


287 days. 


U Cephei, . 


7 „ 


9 


2d. llh. 50m. 


E Andromedae, . 


5-6 , 


, 13 


411 daj's. 


Third 


Class. Fourth Class. 


t, Geminorum, 


3-7 to 


4-5 


10 d. 3h. 41m. .30.S. 


n Argus, 


1 to 7 


About 70 years. 


68 (u) Herculis, . 


4-5 „ 


5-6 


38 d. 12 h. 


T Ceti, 


5 , 


, 7 


About 65 days. 


jS Lyrae, 


3-4 „ 


4-5 


12 d. 21 h. 46 m. 56 s. 


s Aurigae, . 


3 , 


, 4-5 


Very irregular. 


£ Aquilae, . 


3-5 „ 


4-7 


7d. 4h. 14 m. 


E Coronae, . 


6 , 


, 13 


Very irregular. 


T Vulpecdlae, 


5-5 „ 


6-5 


4d. 10 h. 29 m. 


a Herculis, 


31 , 


, 3-9 


From 26 to 60 days. 


B Cephei, . 


3-7 „ 


4-9 


5d. 8h. 47 m. 40 s. 


T ScoRPii, . 


7 , 


, 10 


Irregular. 


E Aurigae, . 


6 „ 


12 


464 days. 


iS Pegast, 


2-2 , 


, 27 


Very irregular. 




Fifth Class (temporary stars). 






DATE OF APPEARANCE. 


IN THE CONSTELLATION OF 


MAGNITUDE. 


July, 134 B.C. 




Scorpio, near jS, . . . 






1st. 


December, 123 B.C. 




Ophiuchus, near a. 


. . 










1st. 


10th December, 173 a. D. 




Centaurus, near a, 


• . 










1st. 


329 A.D. 




Aquila, 


• 1 












March, 369 a.d. 




Unknown, 


. 












April, 386 a.d. 




Sagittarius, near X, 


. 










Very bright. 


„ 389 A.D. 




Aquila, near a, 


• • • 










1st. 


„ 393 A.D. 




Scorpio, 


. 










Very bright. 


„ 827 A.D. 




Scorpio, 


. 










1st. 


„ 945 A.D. 




Between Cassiopeia and Cepheus, 










Very biilliant. 


May, 1012 a.d. (or 1011, 




Aries, .... 










Exceedingly bril- 


or 1006). 














liant. 


July, 1202 A.D. 




In the tail of Scorpio, 










1st. 


December, 1230 a.d. 




Ophiuchus, near Serpens, 










1st. 


July, 1264 A.D. 




Cassiopeia, near Cepheus, . 










Very bright. 


11th November, 1572 a.d. 




Cassiopeia, near x (Tycho's Star), 










1st. 


February, 1578 a.d. 




Unknown, .... 










Very bright. 


1st July, 1584 a.d. 




Scorpio, near •»■, . 










Very brilliant. 


18th August, 1600 a.d. 




Cygnus, near 7, . . . 










3rd. 


10th October, 1601 a.d. 




Ophiuchus, near & (Kepler's Star), 










1st. 


1609 A.D. 




Unknown, .... 










Very briglit. 


20th June, 1670 a d. 




VoLPECULA, near (2 Cygni, 










3rd. 


28th September, 1090 A.D. 




Sagittarius, near t, . 










4th. 


28th April, 1848 a.d. 




Ophiuchus, near ri (Hind's Star), 










5tlL 


1860 A.D. 




T Scorpio in M. 80, . 










7tlu 


12th May, 1866 a.d. 




Corona Borealis, near i. 










2nd. 


24th November, 1876 A.D. 




Cygnus, near f, . . • 










3rd. 


September, 1885 a.d. 




Andromeda, in the centre of the Great Ne 


:)ula, 






6th. 



28 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Such are the so-called "temporary" or "new" stars. These stars from time to time appear suddenly in 
different parts of the heavens, at first being exceedingly conspicuous, and then gradually fading in lustre till 
once more they become invisible. Within historic times there are no less than twenty-seven recorded 
instances of such stars having been seen. The first was observed in the year 134 B.C., and was the means 
of suggesting to Hipparchus the necessity of forming a catalogue of the positions of the more important stars. 
The most conspicuous one of the class, however, did not appear till the eleventh of November, 1572. This 
star is well known as Tycho's star, as that astronomer made many observations of it. It appeared in the con- 
stellation of Cassiopeia, near the small star k, and in a few days' time reached its maximum brilliancy. This 
was equal to the brightness of Venus, and thus the star could be distinctly seen in daylight. It did not long 
remain at this brilliancy, but faded gradually away, till, sixteen months after its appearance, in February, 1574, 
it became invisible. This remarkable object it is believed appeared 308 years previously, or in the year 1264, 
and also in the year 945, or 629 years previously. Thus the star is probably but the member of another type 
of variable stars, whose extensive fluctuations occur in very long and irregular periods. In this particular 
instance, the period of maximum brightness lies doubtless somewhere between 308 and 319 years : so that it is 
not altogether improbable that within the next few years there may be witnessed another sudden appearance 
of the same star. 

During the month of May, 1866, another temporary star suddenly appeared. It shone out in the 
constellation of the Northern Crown, as a star of the second magnitude. The period of visibility in 
this instance was not so long as in the one mentioned above, as this star only retained its greatest 
brightness for about four weeks, and in so short a time as five weeks it disappeared and reached its 
present brilliancy, the ninth magnitude. Fortunately, on this occasion the " new " star could be very 
minutely observed — far more accurately than the star of Tycho. The spectroscope, that powerful instrument 
of modern analysis, could now be advantageously employed {see Plate 19). That wonderful instrument, 
■when applied to the blazing star, showed that it was surrounded with a large quantity of luminous 
gas — gas whose temperature was probably suddenly raised by the downfall of some mighty mass of 
matter. 

The variations of many of the so-called new stars are thus not improbably produced by swarms of 
meteors revolving round them in paths whose perihelia lie very near the stars. Every time, for instance, 
that the cluster passes closely to the star, a considerable quantity of the meteoric matter will, by the 
star's attraction and the retarding influence of its extensive atmosphere, be dragged to its surface. This 
will be sufficient to suddenly raise the temperature of the star, and thereby increase its brightness to 
such an extent as to make it appear a conspicuous object in the heavens. 

Other variable stars, again, especially those of the third and fourth types, may have their fluctuations 
produced by a gradual increase and decrease of the number of sjDots on their surfaces. And so these 
stars may be somewhat like our sun in the variation of his spots, only in a more marked degree ; a 
supposition that seems to be remarkably borne out by the spectra of their light, and, within certain 
limits, the irregularity of their periods. 

STAR CLUSTERS AND NEBULA. 

In various parts of the heavens stars are seen crowded together, forming what are called star clusters. 
Several of these objects can be distinctly seen with the unaided eye, but the greater number require the 
telescope to render them visible. The most conspicuous of the naked-eye groups, the well-known Pleiades, is 
situated in the constellation of Taurus. Plate 6 is a view of this group as taken from a recent telescopic 
photograph. In this cluster, with ordinary eyesight only, six or seven stars can be seen, but with the telescope 
the number increases with the space-penetrating power, and with some instruments over 400 stars can be 
counted. The Praesepe, or Bee-Hive, in Caiscer is another very conspicuous group, and one well seen by the 



I 



Star Clusters — plate 7. 




Nebulae— Plate 8. 




THE SIDEREAL HEAVENS. 



29 



aid of a small telescope ; and also the clusters in Perseus and Gemini. In the constellation of Hercules there 
is situated one of the finest clusters in the heavens (see Plate 7). This extremely beautiful object, of a 
globular form, is estimated to contain no less than fourteen thousand suns. Many of the star clusters are so 
distant, that even with the most powerful instruments they appear simply as faint hazy masses. Whenever 
this is the case, and they cannot be resolved into glittering points, or individual stars, they are called Nebul.*:. 
No less than about seven thousand of these wonderful objects have been discovered. 

Like the stars, these objects are arranged into different classes. First, there are nebulae whose forms are 
exceedingly indefinite, and whose boundaries increase with the power of the telescope employed. The largest 
of this class is well represented by the " Great Nebula " in the sword-handle of Orion, and the " Queen of 
Nebulae " in the constellation of Andromeda. Several of the nebulae of this class are, like the nebulae in the 
Pleiades (Plate 7), so faint that they cannot be seen even with the largest telescopes, and are only rendered 
visible by means of the sensitive photographic plate. Next, there are nebulas, with fairly regular forms, like 
the Dumb-bell nebula in Vulpecula (see Plate 8a), and the Crab nebula in Taurus (see Plate 8). Thirdly, 
several appear to be arranged in a spiral shape, a class which is exceedingly faint, and whose discovery in the 



TABLE OF NUMBER OF STARS OF EACH MAGNITUDE. 



VISIBLE TO THE NAKED EYE. 


ONLY SEEN BY AID OF THE TELESCOPE. 


20 stars of the 1st magnitude 


13,000 stars of the 7th magnitude 


30 million stars of the 


14th 


magnitude 




59 „ „ 2nd 


40,000 „ „ 8th 


90 


15th 






182 „ „ 3rd 


100,000 „ „ 9th 


270 


16 th 


N, 


s 


530 „ „ 4th 


400,000 „ „ 10th 


820 


17th 




c 


1600 ,, „ 5th 


1,000,000 „ „ 11th 


2500 


18th 




>1 


4800 „ „ 6th 


3,000,000 „ „ 12th 


7000 


19th 








10,000,000 „ „ 13th 


22,000 


20th 


" J 


■^ 



year 1846 was entirely owing to the labours of Lord Rosse (see Plate 8h). Fourthly, there are what are 
called annular nebulae — objects like the remarkable one in the constellation of Lyra, that appear in the 
form of luminous rings. And, lastly, there is, perhaps, the faintest class of all, the planetary nebulae — objects 
which appear like large indistinct planets, with either round or elliptical discs. 

These nebulae, as above indicated, were at one time supposed to be simply huge clusters of suns, removed 
to distances so enormous as to give them the appearance of faint cloudy masses. As soon as the spectroscope, 
however, was employed in this portion of sidereal research, it proved beyond a doubt that in many cases the 
nebulae were gigantic masses of luminous gas. These objects, therefore, cannot be huge stellar systems far 
outside our own, but simply comparatively tiny portions, of one great aggregation of a wonderful variety of 
orbs, composing the sidereal universe to which our own sun belongs. This is remarkably confirmed by the 
very arrangement of the nebulae. Like the stars they are not indefinitely scattered over the heavens, but dis- 
tributed somewhat according to law. In the case of the stars this would at first sight seem not to be the fact, 
as a cursory view of the heavens does not reveal the nature of star arrangement. It requires, in fact, careful 
telescopic examinations of the numbers of stars in all parts of the star-sphere, before the manner of distribution 
can be recognised. 

With the unaided eye, as is well known, about six thousand stars only can be seen in both hemispheres, as 

e; 



so A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



represented in Plate 4. This, however, is but a very insignificant portion of the actual number as revealed with 
the telescope. To the naked eye, stars much fainter than the 6th magnitude cannot be seen, but with the 
largest instruments, stars as faint as the 16th and I7th magnitude are rendered visible, as indicated in the 
following Table : — 

STARS VISIBLE WITH TELESCOPES OF DIFFERENT SIZES. 
Diameter of object glass, or speculum, of telescope in inches, h f 1 H 2| 4 6| 10 16 25 40 
Smallest Magnitude of star revealed, . . .7th 8th 9th 10th 11th 12th 13th 14th 15th 16th 17th 

As would naturally be expected, the number increases as the stars diminish in brightness ; consequently, 
while scarcely six thousand stars can be seen with the naked eye, no less than about one hundred millions are 
rendered visible with the largest instruments. The number of stars in each magnitude is given in the Table on 
page 29. Thus it is highly probable that down to the twentieth magnitude — a magnitude at present invisible 
even to the most powerful telescope — there are upwards of thirty thousand millions of stars. As already men- 
tioned, these millions of orbs are not equally distributed in the heavens, but are greatly more condensed in some 
places than in others. In fact, it is found that they increase in number when that luminous great circle of the 
star sphere, the Milky Way, is approached. The nebulae, on the other hand, decrease in as great a propor- 
tion towards the Milky Way, and are densely clustered in two places on the star sphere which are situated 
perpendicularly to that cloudy zone, or in parts of the heavens surrounding its poles. There are, therefore, in 
the heavens two distinct regions — a region of stars lying principally in the plane of the Milky Way, and a 
region of nebuloi situated at right angles to it. This proves that the nebulae undoubtedly belong to our 
sidereal system, and are probably for the most part no further removed than the average stellar distances ; so 
that all the millions of stars revealed by the most powerful telescopes ; the vast numbers of star clusters, each 
containing thousands of suns ; the thousands of gaseous nebulae ; and even the Milky Way with its millions of 
orbs, form only the different parts of one huge and complex system — the sidereal universe. 



THE MILKY WAY. 

This luminous zone can be noticed on any dark and cloudless evening, as a beautiful band of soft light 
stretching completely across the heavens. Its position in the sky as seen in the northern and southern 
hemispheres can be easily found by means of the small circular charts at the end of the volume. In the 
northern heavens it will be noticed that the galactic zone passes near the constellations of Orion, Gemini, and 
Taurus, and completely traverses Auriga, Perseus, Cassiopeia, Cepheus, Cygnus, Vulpecula, Sagitta, 
Aquila and Serpens ; and in the southern heavens, Ophiuchus, Sagittarius, Scorpio, Ara, Centaurus, 
Crux, and Argo, and passes exactly between the constellations of Canis Major and Canis Minor. That part 
of its course extending from Canis Ma.] OR through Auriga to Cygnus, is comparatively faint and of fairly 
regular form. In Cygnus, however, the zone becomes broken up into several gaps, and before it enters 
Aquila it is completely divided into two streams, which continue till the constellation of Scorpio is reached, 
where it is once more united. From this part of the heavens to the place in Argo where the stream is 
completely separated by a curiously-shaped opening, its form is exceedingly complex, and at the same time its 
luminosity is more conspicuous. The Milky Way, or Via Lactea, thus passes completely round the star- 
sphere, and forms on it a luminous great circle, which proves that our sun is interior to it, and within its 
bounds. 

In all ages this zone has attracted considerable attention, and offered for solution one of the noblest 
problems. For centuries the philosopher of old gazed at it in wonder and admiration, as night after night it 
moved over his head in its apparent revolution with the great star dome. Times without number the modern 



PLATE SA. 




< 
Z 

> 
CO 

a 

z 
< 



< 

D 
CQ 
Ui 

Z 

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a: 

a 

CO 
£ 



THE SIDEREAL HEAVENS. 



astronomer has turned his most powerful instruments to it, in the hope of sounding its mio-hiy depths, for in it 
he knows there is locked the secret of the structure of the visible universe. 

To the ordinary observer among the ancients, the Milky M^'ay was simply a large mark in the heavens, 
which had been produced by the soldering together of the two hemispheres ; a dense fire showin"- itself through 
a huge cleft in the celestial vault ; or it was the home which the shades of happy souls inhabit. But while the 
multitude had no difficulty whatever in believing in these absurd imaginations, with the more enlightened 
minds it was greatly different. Though they did not possess, as we now do, the power of penetrating into 
many of Nature's greatest mysteries, and thus could not tell for a certainty of what the Milky Way was 
composed, or what importance it held in the sidereal universe, yet for all that they recognised the greatness of 
the problem that the more thoughtless had solved so easily, and rose to a not unworthy conception of its 
significance. They had, indeed, even concluded that it was composed of myriads of exceedingly faint 
stars. Manilius, their astronomical poet, advocates this remarkable idea — remarkable, indeed, for the time ia 
which it was advanced ; while the description given by Ovid might even have been the production of modem 

thought. He says : — 

" Its. groundwork is of stars, through which the road 
Lies open to the Thunderer's abode." 

But though the more advanced among the ancients might form even sublime ideas as to the nature of 
the Milky "Way, yet, at best, their ideas could only be mere conjectures, for it required far more than man's 
ordinary vision to penetrate the mystery that was hidden within its bounds. It required, in fact, nothing less 
than a gift of second sight — a gift which, even three centuries ago, it would seem impossible for man ever to be 
able to possess. This wonderful gift has now been bestowed. Galileo, by his immortal invention, has enabled 
man to lift, in some measure, the veil which for long ages had obscured the wonders and beauties of the 
outside universe, and to look behind it far into the infinite depths of space, and see what was going on 
amongst the countless systems of suns and planets which surround us on every side. 

It was not, then, until the newly-invented telescope had been turned to this great luminous zone, which 
had for so many centuries puzzled mankind, that its true nature was revealed. What Galileo saw, every one 
possessing even so small an optical instrument as an opera-glass, can see — viz., that the misty light of the 
Milky Way is in reality produced by the combined lustre of myriads of exceedingly faint stars. As the 
telescope rapidly improved, the structure of the Milky Way became more and more thoroughly examined. 
Sir W. Herschel was one of the first to make this grand star-stream the object of careful study. Sweeping 
it with his powerful reflectors, he penetrated to much vaster depths than any one before him had done, 
and even discovered the individual stars composing those faint clusterings, which -with inferior instruments 
appear only as cloudy patches, like the Milky Way to the unaided eye. But even when all this had been 
accomplished, when mighty depths had been sounded and enormous numbers of orbs had been revealed, there 
still remained in the background other, though certainly smaller, parts which could not even with his most 
powerful telescope be completely resolved into stars. 

The total number of stars distributed along the Milky Way must thus be so excessively great as to be 
altogether beyond our conception. On a photograph of a small portion of it recently taken by the author mtli 
a lens of not over four inches in diameter, and with an exposure of only three hours, more than one thousand 
stars can be counted; while, with one of Herschel's large reflectors, the number of stars was very great indeed. 
On one occasion, Herschel tells us, he allowed his instrument to remain stationary, so that the stars would, 
by the rotation of the earth, be made to pass through the field of view, and, in doing this, he found that, in 
so short an interval as one quarter of an hour, no less than one hundred and twenty thousand stars passed 
before his eyes ; from which he concluded that there were, at least, tiventy millions of stars in the Milky 
Way alone. 

The stars composing this wonderful zone are evidently much smaller and lie at greater distances than 



32 



A POPULAR HANDBOOK AND A'TLAS OP ASTUONOMY. 




Fig. 15. THE MILKY WAY 
AS VIEWED WITH A TELESCOPE. 



the stars in other parts of the heavens. To Herschel, and others of his time, it seemed that this luminous 
belt was simply the effect produced by looking from near the centre towards the edge of a vast collection 
of orbs, and viewing great depths of stars ; for it was supposed that these orbs were approximately of one 
size, and were fainter or brighter according to their difference of distance from our system. This, how- 
ever, cannot by any means be the fact. The stars are, in many cases, not fainter or brighter owing to 
difference of distance, but to actual difference in size. Observation has now revealed to us that several 
of the brighter stars arc removed to enormous distances, while one or two of the fainter orbs are 

comparatively neai\ Thus the Milky "Way cannot receive its appear- 
ance from the combined light of large stars removed to enormous 
distances, but from a gigantic aggregation of comparatively small 
orbs. 

But though these orbs composing the Milky Way are apparently 
small, we must not on this account think that they are very insignificant, 
or, though seemingly close to each other, that they are so in reality. 
Each small twinkling point of light is a sun ! a sun, it may be, not 
very much smaller than ours ; and, though these suns are apparently 
touching, they are yet separated from each other by vast distances — 
distances that, in all probability, can only be reckoned by hundreds of 
millions of miles. Still farther, these stars are not only suns — 
they are doubtless the centres of planetary systems ; for as our sun, 
and each of the larger suns already considered, is the centre of a wonder- 
ful and extensive system of planetary globes, so is every one of the faint stars in the Milky Way the centre 
of a similar system of worlds. Each is, in fact, the centre of all force, all light, and all life to its system ; 
upon whose munificent supplies the existence of intelligent beings may depend. 

Looking at the Milky Way as it stretches across the heavens, and contemplating its grandeur, we are 
thus carried by imagination far from the busy scenes of earth, away into the mighty depths of space, amidst 
the splendour of suns and the rush of systems ; and are led to think of the utter insignificance of the whole 
solar family, of our world which oftentimes seems so gigantic, and even of man himself, for we cannot believe 
that these glorious orbs have been called into existence for the purpose of rolhng uselessly through endless 
space. Modern astronomy, by its wonderful discoveries, though unable to tell us directly that there are other 
inhabited earths besides our own, has certainly shown us that the universe is the production of one thought ; 
that one plan runs throughout all that has been revealed. If, then, other suns and other earths have been 
created — as they have undoubtedly been — it is not altogether unreasonable to suppose that, as they have been 
produced by the same great laws as our own sun and our earth, they have been formed for similar purposes. 
A unity is thus recognised to exist between the most distant parts of space ; yet along with this unity there is 
the most wonderful variety. Even in the whole sidereal universe, with its millions of millions of orbs, it is 
highly probable that no two are exactly alike. Each, certainly, has been formed under the same mysterious 
laws ; on each the same forces and processes are at work ; yet on each the outcome of these laws, these forces, 
and these processes may be greatly different ; and so with Byron we say — 

" Ye stars ! which are the poetry of heaven ! 

. . . Ye are 
A beauty and a mystery, and create 
In us such love and reverence from afar 
That fortune, fame, power, life, have named themselves a star." 



Plate 8b. 




The Dumb-bell Nebula as seen by Lord Rosse. 




Nebulae as seen by Sir J. Herschell. 



£^ 



CHAPTER IV. 

THE SUN. 

'• Siro of the seasons ! Monarch of the climes, 
And those who dwell in them ! for near or far 
Our inborn spirits have a tint of thee, 
Even as our outward aspects ; — thou dost rise^ 
And shine, and set in glory." — Byron. 

ITS DISTANCE FROM THE EARTH. 

Till within comparatively recent times much error existed regarding the distance and size of the sun. 
Both of these are now known with certainty, and greatly exceed previous ideas. One of the first attempts to 
determine the true position which the sun occupies in the universe was made in the year 270 B.C. The 
philosopher Aristarchus of Samos, in that year, from observations of the moon when half enlightened, tried to 
measure the sun's distance, and though he was not so successful as might have been desired, he nevertheless 
increased the supposed boundaries of the universe, by proving that the sun was certainly much more distant 
and gigantic than the moon. About four hundred years afterwards, ad. 138, the celebrated Alexand^' ,u 
astronomer, Ptolemy, likewise attempted the measurement of the sun's distance, and concluded that il .vas 
considerably greater than Aristarchus had believed ; stating its distance at about five millions of miles. This 
distance of Ptolemy's was considered so enormous that for over fourteen centuries afterwards it was 
believed to be approximately accurate. The first alteration of this distance was made by Kepler in 1G18, who 
held that the sun was distant from the earth about fourteen millions of miles. In fact, by each attempt to 
measure the distance of the sun, it was proved that it was in reality greater than either the instruments or 
methods employed were capable of determining. The following Table shows the distance of the sun 
according to ancient astronomers. 

DISTANCE OF THE SUN ACCORDING TO ANCIENT ASTRONO]\rERS. 



DATE. 


ASTRONOMER. 


DISTANCE. 


DATE. 


ASTRONOMER. 


DISTANCE. 


270 B.C. 
130 B.C. 
138 A.D. 


Aristarchus 
Hipparclins 
Ptolemy . 


3 millions of miles. 
3 >> )) 


1543 A.D. 
1602 A.D. 
1618 A.D. 


Copernicus 
Tycho Brahe 
Kepler 


2 millions of miles. 
14 „ 



It was not till the year 1672 that the more modern method of determining the distance of the sun, from 
the known distance of some planet nearer to us than that orb (such as Venus, or Mercury), was successfully 
employed. From numerous observations of the planet Mars, made in both hemispheres, the astronomer 

33 



34 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Cassini found that the sun was distant from the earth at least eighty-five millions of miles, or actually six 
times further away than had been supposed from observations made by Kepler fifty-four years previously. But 
even this great increase of the ancient determinations is actually too small. From all the different methods 
that have been employed, it is now considered that the sun's true, average, or mean distance is very nearly 



MODERN DETERMINATIONS OF THE SUN'S MEAN DISTANCE. 



YEAR. 


ASTRONOMER. 


METHOD OF DETERMINATION. 


DISTANCE. 


1672 A.D. 


Cassini, . 


From the parallax of Mars, 


86,000,000 mdes. 


1770 


Euler, . 




„ transit of Venus of 1769, . . . 




92,897,000 


)> 


1771 


Lalande, 




)> >> )> )) • • • 




95,835,000 


» 


1772 


Pingr^, . 




11 )) )) )) • . • 




92,790,000 


») 


1804 


Laplace, . 




observations of the variation of the displacement 
moon, depending on the sun's distance, . 


3f the 


95,057,000 


)) 


1814 


Delambre, 




the transit of Venus of 1769, 




95,613,000 


)) 


1823 


Enchi, . 




1761 and 1769, 






95,279,000 


J) 


1832 


Plana, . 




observations of the moon. 






94,725,000 


>) 


1862 


Foucault, 




the measured velocity of light, 








92,268,000 


>) 


1864 


Hansen, . 




,, displacement of the moon. 








91,647,000 


)) 


1867 


Newcomb, 




,, parallax of Mars, . 








92,372,000 


)) 


1872 


Le Verrier, 




,, masses of the planets, 








92,268,000 


)) 


1875 


Galle, . 




„ asteroid Flora, 








92,163,000 


:) 


1877 


Cornu, . 




,, velocity of light. 








92,897,000 


)) 


1877 


Airy, . 




,, transit of Venus of 1874, 








93,321,000 


j> 


1878 


Stone, . 




)) » )» )) < 








92,060,000 


» 


1878 


Tupman, 




)) )> )) >» 








92,372,000 


>) 


1878 


Maxwell Hall, 




„ parallax of Mars, . 








93,002,000 


)) 


1881 


Puiseux, 




,, transit of Venus of 1874, 








91,035,000 


)) 


1888 






,, British observations of the transit of Venus of 1882, 


92,581,000 


)» 


1888 






„ American photographs „ ,, „ „ 


92,372,000 


») 



92,897,000 miles — a distance that is probably accurate within 200 thousand miles. This distance is so 
enormous that an express train, travelling continuously at the velocity of sixty miles per hour, would require 
nearly 177 years to journey over it. Even light occupies a sensible interval in darting across this mighty void 
lying between us and the great centre of the system. Each minute this swift messenger journeys over a 
space of eleven millions of miles, yet the distance of the sun is so great that it requires no less than 8 minutes 
19 seconds to travel from him to our earth. 



THE SUN. 



35 




Fig. 16. diagram showing ratio of 
the orbit of the moon to the 
diameter of the sun, a b. 



SIZE OF THE SUN. 

The distance of the sun being so enormous, proves that he is a globe of gigantic size. To all appearance 
he is about the same size as the moon, having an apparent diameter of about half a degree. His actual 

diameter will thus be as many times larger than that of the lunar globe 
as his distance from us is greater than that of our satellite. If, for instance 
as was once supposed, the sun's distance is only twenty times greater than 
that of the moon, then his diameter would only exceed the lunar diameter 
in the same proportion. The distance of the sun, however, is known to 
exceed the distance of our satellite over 387 times, and this will be the 
approximate proportion between the diameters of the two globes. The 
actual diameter of the solar globe is, therefore, no less than 860,500 miles 
— about 110 times greater than the diameter of the earth, or nearly 
twice longer than the diameter of the lunar orbit. The sun accordingly is 
an orb in size so gigantic that if the earth were placed in its centre, the 
moon could revolve in her orbit at her ordinary distance from us, and 
still be well within the solar globe (see Fig. 16). But if the difference 
between the solar and terrestrial diameters is striking, there is even a greater 
contrast between the surfaces and volumes. The surfaces of sflobes are in 
proportion, not to their diameters, but as the squares, and the volumes of globes, as the cubes, of their 
diameters. While, therefore, the diameter of the .sun exceeds that of our globe 110 times, in surface it 
exceeds the earth twelve thousand, and in volume, or cubic capacity, one and a-third million of times. 

If, however, the volume of the solar globe is so enormous, its comparative weight, or mass, is not so 
marked. Owing to the inten.sity of the heat, the materials of which the sun is composed are not nearly of so 
great a density as those forming our earth. The average density of terrestrial material is about five and a-half 
tiipes that of water, but that of the sun, only one and a-half times.* While, therefore, one and a-third millions 
of earths would be required to form a globe equal to the sun in volume, 332 thousand only would equal 
the sun in mass. The amount, however, of this comparatively light material is so considerable, that, not- 
withstanding the great distance of the surface of the solar globe from its centre, the attraction of gravity on 
the surface is actually twenty-seven and a-half times greater than on earth, so that the weight we call a pound 
would, if removed to the solar surface, weigh twenty-seven and a-half pounds.-[- This increase of gravity on 
the sun's surface, in comparison with the attraction on our globe, notwithstanding that its distance from the 
centre is 110 times greater than in the case of our earth, shows that the total force of the sun is enormous ; 
for the force, or attraction, of a globe is always in proportion to its mass. By it the various gigantic planets 
and comets of our system, as well as the tiniest meteorites, are kept revolving round this centre ; moving in 
paths that in some cases are so wide that light occupies hours in journeying aci'oss them, and with velocities 
many times greater than that of a cannon-ball. 



SUN-LIGHT AND HEAT. 

Whilst the attraction of the solar orb is felt even at the remotest parts of the planetary system, if not 
among the nearer stars themselves, his light and heat will be influential there also. The quantity, or 
total amount, of light which the sun is constantly radiating into space is truly inconceivable. The intensity, 

* The density of a globe, as compared with that of the earth, is determined by dividing the total quantity of matter it 
contains, or its mass, by its volume. 

t The attraction of gravity on the surface of a globe is found by dividing the mass by the square of the distance from it§ 
surface to the centre — or by the square of its radius, 



36 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



however, or the comparative brilliancy of the solar surface with that of terrestrial luminous standards, can be 
approximately estimated. It is so great that even at a distance of 93 millions of miles, the sun actually 
appears 600 thousand times more brilliant than the full moon. In fact, it has been ascertained that, at the 
sun's surface, the light is no less than 90 thousand times brighter than a candle flame ; five thousand times more 
brilliant than the dazzling radiance of molten iron; 150 times brighter than the lime-light; and three times 
more intense than the brightest attainable terrestrial light — the wonderful electric arc. The quantity and 
intensity of solar heat is likewise exceedingly great. It has been ascertained that during each hour every 
square yard of the sun's enormous surface radiates into space as much heat as could only be produced by the 
combustion of nine tons of coal ; or to keep up the supply of solar heat it would require a shell of coal 
about twenty feet in thickness surrounding the sun, to be consumed every hour. 

This vast quantity of light and heat constantly radiating from the sun into space cannot, as was formerly 
supposed, be maintained by any process of combustion. If the sun had been a huge ball of burning coal 
ignited six thousand years ago, it would by this time have burnt out and become a black mass. Neither can 
the maintenance of the light and heat be accomplished by the downfall of meteoric matter. If this were 
the case it would require as great a quantity of matter as there is in the moon, to fall into the sun every 
year. This amount of meteoric material, it is known, does not annually fall into the sun, so that it is neither by 
combustion nor by the precipitation of meteors that the solar light and heat are maintained. It is not, 
however, at all necessary that either of these processes should exist in order to supply the great loss of heat 
constantly taking place from radiation. By the mutual attraction of the gaseous particles of his globe, the sun 
has within himself the means not only of supplying what is lost by radiation, but of actually increasing his 
temperature. From the gradual contraction of his globe, enormous quantities of heat are being generated. 
Like all falling bodies whose forces are arrested, the various molecules composing the solar mass are, in being 
attracted towards the centre of the sun's globe, generating heat, and slightly more heat than is being radiated 
into space. In maintaining the supply of light and heat, the sun, from the contraction of its particles, is 
gradually decreasing in size. At present the yearly amount of subsidence of the vapours on the solar surface 
is thought to be about fifty yards, so that the diameter of the sun is annually decreasing by about one hundred 
yards. This decrease, however, cannot go on continually, but will sometime cease ; then radiation will gradually 
cool the huge fiery globe, until it becomes a dark ball — a dead sun rolling through space. 

SUN-SPOTS, ETC. 

As soon as the telescope was directed to the sun it was discovered that his surface contained several dark 
spots. From a study of the manner of appearance and disappearance of these objects it was found that, like our 
earth, the sun rotated on his axis, and in the same direction, from west to east. It was noticed, however, that, 
unlike our globe, the sun does not turn all of a piece, but the more distant a part of the surface is from the 
solar equator, the slower its rotation. Near the equator, for instance, the rotation is accomplished in about twenty- 
five days ; midway between the equator and the poles it is about twenty-seven days ; while nearer the poles 
it is longer still. This proves that the sun's globe cannot be solid, but liquid, or rather vaporous, even to the 
centre. 

It is noticed that the spots which apparently move across the solar disc from the rotation of his globe, ^M 
are always confined to certain regions. Near the equator, spots are rarely noticed, and at the poles they are 
never seen, but seem located in two zones on the solar surface about twenty degrees in breadth, lying 
on either side of the equator. It is found, too, that the number of spots is not always, even approximately, 
the same. At times, no spots can be seen on any part of the surface, while at other times large 
numbers are visible. The number of spots, in fact, regularly passes from a maximum to a minimum, and 
back to a maximum again, in a period of about eleven years. This variation, which is simply an index of 



The Sun — Plate 9. 




THE SUN. 



the variation of solar activity, is, strangely enough, in some way connected with the variation of the magnetic 
needle, for when the sun's activity is at a maximum, the diurnal movement of the compass is then greatest. 

At first it was thought that sun-spots were simply quantities of slag or scoriae floating on the molten 
photosphere. Careful observations, however, have proved that this is far from being the case, as sun-spots are 
in reality enormous cavities. The blackness of a spot is produced by the light, which comes from the bottom 
of the cavity, being greatly diminished by absorption from the great depth of comparatively cool vapour with 
which the spot is filled. In fact, even the darkest part of the spot, or the umbra, is self-luminous, and shines 
with a brilliancy greater than that of the lime-hght, and it is only by contrast with the exceedingly intense 
light of the surrounding surface that it appears dark. These spots, generally of an enormous size (see Plate 9), 
are continually undergoing great variation in shape and dimension. Within each spot, tremendous disturbances 
are continually taking place, the spots themselves being simply the outcome of the fierce cyclonic storms, which 
are always to some extent raging on nearly every part of the sun's gaseous surface. By means of these gigantic 
maelstroms, as revealed in the spots, the comparatively cool vapours of the surface are sucked far down into 
the interior, where they are heated, and, in the form of ejections, returned to the surface. This circulating 
action of the solar vapour is of the greatest importance in preserving the life and activity of the sun ; for by 
it a solid crust is prevented from forming, and the solar globe from rapidly cooling down. 

Besides dark parts or spots, there are portions which in appearance are considerably brighter than the 
general luminosity of the surface. These brighter portions are called faculae (see Plate 9). Unlike the spots, 
the faculae are seen on every part of the disc, but are more conspicuous near the sun's edge. This is owing to 
the effect of contrast, which is greater there, as the edge of the disc is considerably less brilliant than the 
centre. The faculae are believed to be nothing more than gigantic eruptions of comparatively light, but much 
more intensely-heated vapour, such as glowing hydrogen, which are momentarily taking place on all parts of 
the surface. Seen with very high telescopic powers the disc has a peculiarly granulated or mottled appear- 
ance. The largest markings are known as rice-grains, and the small ones as granules. Like the faculae, 
but on a very much smaller scale, these markings seem to be clouds of intensely hot and bright gases 
suspended in a slightly darker atmosphere. 

TdE sun's INTEKIOR. 

That portion of the sun from which we receive our light — the visible surface, oi the photosphere— is 
simply a shell of glowing vapour about 10,000 miles in thickness. Below this region there is the gigantic 
central ball of the sun, 850,000 miles in diameter, about which astronomers know httle or nothing, beyond the 
fact that it cannot be solid. From the intensity of the internal heat, it is known that even the centre of the 
sun or the densest part of the solar globe, notwithstanding the enormous pressure to which the particles com- 
posing it are subject, consists of some gaseous material, though the vapour there is doubtless, from the 
pressure, as heavy as the densest of our metals. 

SOLAR ATMOSPHERE. 

Lying immediately above the photosphere, and extending outwards to an unknown distance, is the sun's 
so-called atmosphere. This atmosphere, completely surrounding the solar globe, is in nature exceedingly 
complex. Its base, extending from the visible surface for about one thousand miles, is chiefly composed 
of the heavier metallic vapours, such as the vapour of iron, copper, zinc, &c. Above this layer the uncondensed 
gases are much lighter, and consist principally of hydrogen. This part extends upwards to about 10,000 
miles, and from its coloured appearance is called the chromosphere. In it the most wonderful changes arc 
ever taking place. Eruptions are constantly projecting monster jets of hydrogen gas, mixed with metallic 
vapour, to great heights, sometimes to over 100,000 miles. Generally these prominences, as they are 
designated, are of a blood-red colour, and can only be seen either by aid of the spectroscope, or during a 
total solar eclipse. 



38 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Beyond this region the so-called outer atmosphere begins. This is also well seen when the brilliant disc 
of the sun is hidden by the moon in an eclipse. In appearance it resembles a crown of glory surrounding the 
apparently extinguished sun, from which it has been called the " corona." The material of which the coronal 
part of the solar atmosphere is composed is exceedingly light, and is doubtless of a very complex nature. The 
inner part, extending to about 300,000 miles from the visible surface, is thought to be principally gaseous, its 
material being chiefly formed by the gigantic eruptions, which carry vast quantities of vapour to enormous 
heights. The outer part, on the other hand, is believed to be largely composed of solid particles, and is thus 
likely to be of meteoric origin — being probably produced by the materials of dissipated comets and meteor 
streams drawn towards the sun by his mighty attraction, and caused to shine, partly by inherent light from 
the sun's intense heat, and partly by reflecting the sun-light. 

But though the corona does not apparently extend much beyond 300,000 miles from the sun, as observed 
in solar eclipses, it has nevertheless been traced to a considerably greater distance. The rarer, and more distant 
portion, extends, in fact, so far from the sun as to appear in the sky long after sunset, or before sunrise, and is 
known as the zodiacal light. Indeed, this portion of the sun's atmosphere has been noticed extending from 
the sun to a distance of no less than about 100 millions of miles — a distance greater than that which separates 
the earth from the gigantic centre of the solar system. Very probably, however, it reaches even to the path 
of the most distant planet ; so that not only our earth, but each member of the system, in its orbital journey, 
moves through part of this mighty envelope which surrounds the sun. By it the motions of the various orbs 
will be slightly retarded, and drawn gradually nearer to the centre, until ultimately they become united with 
the sun himselfi 



PRINCIPAL FACTS ABOUT THE SUN. 



The mean distance of the sun, which is employed throughout this work, 
Nearest distance of the earth from the sun (in January), . ... 
Greatest distance of the earth from the sun (in July), .... 
The variation of the earth's distance from the sun thus amounts to 

Length of the sun's actual diameter, 

Proportion between the diameter of the sun and that of the earth, 
Surface of the sun compared with that of the earth, . . . . . 
Volume, or cubic contents, of the sun compared Math the earth, . 
Mass, or quantity of matter, of the sun compared with the earth, . 
Average density of the solar globe compared with that of the earth. 
Average density of the solar globe compared with that of water, . 
Attraction of gravity on the sun's surface compared with that on the earth, . 
Inclination of the axis of the solar globe to the plane of the earth's orbit, 
Period of the sun's rotation at the equator, 

latitude 20° 

•if)" 
>> » )) ») )) ^" > ...... 

4-5° 
» )) )i )) )) ^" ) ...••. 

Linear velocity of the sun's equator per second, 








92,897,000 miles. 
91,347,000 „ 
94,447,000 „ 
3,100,000 „ 
866,500 „ 
110 to 1. 
12,000 
1,300,000 
332,000 
0-255. 
1-41. 
27-6. 
82° 45'. 
25 days. 
25-76 days. 
26-5 „ 
27-5 „ 
1-26 miles. 




I 



CHAPTER V. 

THE FLANETABY SYSTEM. 

" "World beyond world, in infinite extent, 
Profusely scattered o'er the void immense, 
Show me their motions, periods, and their laws." — Thomson. 

As mentioned in the last chapter, the sun occupies the centre of the planetary system, producing and regulat- 
ing the movements of all orbs lying within the sphere of his mighty attraction, and bountifully supplying them 
with his light and heat. These orbs, revolving round him, constitute the solar family, which consists of 
eight large planets and numerous smaller ones, divided into distinct classes, revolving in orbits widely 
separated from each other. The eight principal orbs are separated into two groups, which may be designated 
inner and outer planets; while revolving between these are the tiny orbs of the system — the asteroids, or 
small planets. The planet lying immediately outside the orbit of our earth is the most distant member of the 
inner group from the sun — the planet Mars ; while the nearest member of the outer planets — Jupiter — is 
situated at a distance from the central orb no less than five times that of the earth. In the order 
of their distances from the sun, the inner planets are Mercury, Venus, the Earth, and Mars ; and the 
outer planets, Jupiter, Saturn, Uranus, and Neptune. There are, therefore, in the planetary system, three 
different groups of orbs. First, there is the inner, or terrestrial group, from Mercury to Mars, of which our 
earth is the largest member ; second, the small planets, or asteroids, revolving between the orbits of Mars and 
Jupiter ; and third, the outer, or giant planets, from Jupiter to Neptune, of which Jupiter is by far the 
largest. 

Amongst the various members of these classes of planets there exists the most striking difference, in 
dimensions, in weight, and in condition. Jupiter, for instance, exceeds our earth, the largest of the inner 
planets, no less than 1300 times in volume, and is actually larger and heavier than all the other planets j^ut 
together. In a greater proportion even, our globe exceeds the largest of the asteroids (see Plate 10). In 
density, or comparative weight of material, there is likewise a marked contrast. The average density of the 
inner planets (about five times greater than that of water) is much greater than that of the outer orbs. 
The outer planets, on the other hand, are, on the average, about the same density as that of water. 
With regard to the velocity of rotation, there is also a considerable difference. Notwithstanding their enor- 
mous size, the outer planets rotate very rapidly ; while the inner orbs perform their rotations in comparatively 
slow periods. But even in their present physical constitution there exists a marked contrast. The members 
of the inner group are chiefly solid globes, which, from their comparatively insignificant dimensions, have long 
since cooled from their former hot and molten condition, and are rapidly approaching that stage in each orb's 
existence that may be called planetary old age. The outer planets, on the other hand, are mostly red-hot 
masses, surrounded by dense atmospheres, and fitly represent planetaiy youth, or the fiery condition of an orb 
before radiation has accomplished the process of cooling. 

3d 



40 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



THE PLANETS NEAREST THE SUN. 

Though Mercury is undoubtedly the nearest large planet to the sun, several other orbs are believed 
to revolve within his path. No less than twenty of these intra-Mercurial planets are recorded as having 
been seen crossing the sun's disc in transit as dark spots. As, however, the observers of these supposed orbs 
have not, in most cases, been experienced astronomers, the so-called discoveries have been rejected. The 
largest of these planets has been called Vulcan. It was believed to have been seen crossing the sun's disc in 
the year 1859; but if this had really been the case it ought to have been noticed shining as a star during 
every subsequent total solar eclipse. This has not been the case. During each total eclipse of the sun since 
the year 1859, careful search has been made for the planet, and yet it has not been observed, a fact which 
clearly proves that VULCAN does not really exist. 

But if a large planet, such as Vulcan was supposed to be, does not revolve between Mercury and the 
sun, several very small orbs, interior to the path of Mercury, have been discovered. These have not been 
seen as in the case of Vulcan, crossing the solar disc in transit, but have been detected on several occasions, 
as small stars shining near the sun when totally eclipsed. The orbs thus discovered are believed to be the 
largest members of a small ring of tiny planets, somewhat like the so-called ring of asteroids revolving between 
the orbits of Mars and Jupiter, 



Mercuey. 

"Thou little sparkling star of even, 
Thou gem upon an azure heaven ! " — Maria Davidson. 

Mercury, then, is the first important planet outward from the sun. Owing to his proximity to the solar orb 
it is extremely difficult to perceive this planet, as he is nearly always hidden by the overpowering brilliancy of 
the sun's rays. Being nearer the sun than our globe, his path is considerably smaller than the orbit of the 
earth. In fact, the path of Mercury is so much smaller than the terrestrial orbit, that if he journeyed only at 
the same velocity as our globe, or at about eighteen miles per second, he would accomplish his revolution in 
about 141 days. The motion of the planet in its orbit, however, is much more rapid than in the case of our 
earth, and, therefore, a revolution is completed in 88 days, which is the length of this planet's short year. 

The distance of the planet from the sun, notwithstanding the rapidity of its revolution, is considerable. 
On the average it is situated at a distance of about thirty-six millions of miles. As indicated in Plate 11, the 
planet's orbit is not circular, but very elliptical, more so, indeed, than that of any other large planet. This 
ellipticity of the path is in fact so great, that, when traversing one part of it. Mercury is actually fifteen 
millions of miles nearer the central orb than when moving at the diametrically opposite part. When nearest 
to the sun his distance is twenty-eight and a-half millions of miles, while it is increased to forty-three and 
a-half millions when at his farthest from the sun. On account of this great variation of distance from the 
centre of attraction, there results a considerable range of orbital velocity. When moving in perihelion, or in 
that part of his path which lies nearest to the sun, the planet's velocity is no less than thirty-five miles per 
second ; while, when moving at his greatest distance from the solar orb, or at aphelion, it is reduced to about 
twenty-three miles per second. 

The supply of light and heat which the planet receives from the sun, varies in even a greater proportion. 
The amount of light and heat does not decrease directly as the distance from the luminous source increases, 
but as the square of the distance. While, therefore. Mercury, from being nearer to the sun than our globe, 
receives on the average seven times more light and heat than is received by the earth, yet, from the gi-eat 
alteration of his distance, this quantity is subject to a variation in the proportion of nine to four. 

Mercury is the smallest member of the inner planets. His diameter is only two-fifths of the earth's, or 
about three thousand miles. The surface of his globe is thus only one-seventh of the terrestrial surface, and 
his volume about one-eighteenth. Therefore, Mercury is a globe eighteen times smaller than ours, and only 
three times larger than the moon. The materials, however, of which he is composed, are much heavier than 
those forming our earth, or, indeed, of any other planet in the system. In fact Mercury is, curiously enough, 
about the same weight as if he were formed solely of metal of the same name ; for his density is believed to be 
about two and a-half times greater than that of our globe, or about twelve times greater than the density of 
water. Mercury, then, while being the smallest of the primary planets, is, in proportion to his dimensions, by- 
far the heaviest of them. In size he is only about one-eighteenth of the terrestrial globe, while in total weight, 
or mass, he is actually one-eighth of the mass of the earth. 

When this small planet is examined with a telescope it is found, when revolving round the sun, to 
undergo all the phases of the moon (see Plate 15). When close to the sun, and nearer to us than that 
luminary, it appears as a slender crescent. Each day as the planet, from its orbital motion, travels to the 
westward of the sun's disc, this brilliant crescent increases in breadth, till, when at its greatest appai-ent 
distance from the sun, it is seen as a half-illuminated disc. From this position, the greatest western elongation, 
the planet now appears gradually to approach the solar orb. Its distance from the earth increases and its 
apparent diameter becomes in consequence smaller and smaller, and at the same time more of its lighted side 

41 



42 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



is directed towards our globe, till it arrives once more near the solar disc. When further away from us than 
the sun it appears as an exceedingly small and perfectly round disc. This position is called superior 
conjunction, which is exactly opposite to that part of the orbit occupied by the planet when exactly between 
us and the sun, or at inferior conjunction. When in this latter position it sometimes happens that the 
planet is likewise not very distant from the node of its orbit, or that part of its path which cuts the ecliptic 
plane. From being then situated on nearly the same level as the solar globe and the earth, it can be seen 
projected on the sun's disc, and observed to move across, or transit, the sun as a dark spot. The transits of 
Mercury which have taken place since the first one was observed, as also those which will occur till the end 
of the next century, are as follow : — 



TEANSITS OF MERCURY. 



THOSE THAT ARE MARKED WITH AN ASTERISK HAVE NOT BEEN OBSERVED. 



TEAR. 


MONTH. 


YEAR. 


yiONTH. 


YEAR. 


MONTH. 


YEAR. 


MONTH. 








*1710 


Nov. 


6 


1802 


Nov. 


9 


1907 


Nov. 12 








1723 


Nov. 


9 


*1815 


Nov. 


12 


1914 


Nov. 6 








1736 


Nov. 


11 


1822 


Nov. 


5 


1924 


May 7 








1740 


May 


2 


1832 


May 


5 


1927 


Nov. 8 


1631 


Nov. 


7 


1743 


Nov. 


5 


1835 


Nov. 


7 


1937 


May 10 


*1644 


Nov. 


8 


1753 


May 


6 


1845 


May 


8 


1940 


Nov 12 


1651 


Nov. 


2 


1756 


Nov. 


6 


1848 


Nov. 


9 


1953 


Nov. 13 


1661 


May 


3 


1769 


Nov. 


9 


1861 


.Nov. 


12 


1960 


Nov. 6. 


n664 


Nov. 


4 


*1776 


Nov. 


2 


1868 


Nov. 


5 


1970 


May 9 


1677 


Nov. 


7 


1782 


Nov. 


12 


1878 


May 


6 


1973 


Nov. 9 


1690 


Nov. 


10 


1768 


May 


4 


1881 


Nov. 


8 


1986 


Nov. 12 


1697 


Nov. 


3 


1789 


Nov. 


5 


1891 


May 


9 


1999 


Nov. 24 


1707 


May 


6 


1799 


May 


7 


1894 


Nov. 


10 







The most noticeable feature in all telescopic views of Mercury is the marked irregularity of the termina- 
tor or boundary between the light and dark part. This proves that the surface of the planet cannot be 
smooth, but broken up by numerous mountains. Even a more wonderful discovery, however, has been made. 
Like our earth. Mercury has been found to be surroimded with an extensive atmosphere, which contains large 
quantities of watery vapour. This clearly indicates the presence of water on the surface of the planet; 
so that besides mountains, there are oceans and continents. Still further, it is not improbable that some form 
of life exists there. 



\ 



The Orbits of the Inner. Planets — Plate 11. 



\ \ V v 



\ \ V \ \ \ \ \ \ ^ \ ^ M M ^ ' ' ' 1 ' ' ' 



_n_ 



\ \ \ \ \ \ \ \ \ I I I I I j I I I 1 1 I I I I ^ > / ^ / 

'BeliocentiJc Longitu^ in Si^i£ and Pe^r* / 



7™: 



ORBITS OF PLANETS mTEKIOR to ¥ARS 



S(iale o£ Wlions of Mfles 



The position of eaxiTi planet iai its 
orliit is for January T.' 1890 



The divuums alonf the orbits JTiduaU^u potiUmu of Ou, plaiutM i 
ORBIT OF MARS 



V 

V / / // / 



// 1 1 / I 1 1 1 I 1 1 



First 

I / I I I I I I I I ' I I I ^ I i i 




Fomt 
Aries 

1 1 n 



10 ■ " \ \ 



<M«Xil^</ .^imra^ 



Bngj'ayctL liy Archihold. &Fe^ Hdui.'. 



V E N" U S. 

' Fairest of stars, last in the train of night, 
If better thou belong not to the dawn, 
Sure pledge of day, that crown'st the smiling morn 
With thy bright circlet, praise him in thy sphere." — Milton. 

This planet is, to the unaided eye, the most beautiful of all the heavenly bodies. In ancient times it 
attracted considerable attention, and centuries before the true system of the universe was recognised, its 
curious movements among the stars had been carefully observed. As these movements came to be noted, it 
was found that the bright evening star (which was called Hesperus or Vesper) was not always visible, but 
made its appearance at regular intervals. When first detected it was invariably situated in a part of the 
heavens very near to the sun's bright disc. Each evening it travelled farther and farther away from the solar 
orb, till it reached a certain distance from him. It then began gradually to approach the sun, becoming at the 
same time brighter and brighter, till it finally travelled so close to him as to become lost in his brilliant rays. 

But while a conspicuous evening star appeared in the western sky at regular intervals, there was also 
seen, from time to time, a brilliant morning star. This orb (which received the name of Lucifer or Phos- 
phorus) behaved itself in a manner similar to Hesperus, only its movements, with respect to the sun, seemed 
to be performed in reversed order. Instead of being visible in the western sky, and setting after the sun, it 
was seen in the east before the solar orb had yet appeared. When first it became visible it was always 
exceedingly brilliant, and, like the evening star, it was situated very close to the solar globe. Like Hesperus, 
too, it was noticed from day to day to be more and more distant from the sun, till it reached its farthest, 
then began to return to the position it occupied Avhen first detected shining amidst the solar rays. 

Now, as these conspicuous stars, Hesperus and Lucifer, began to be more carefully observed, it was found 
that when the former was visible in the evening, the latter was invisible in the morning ; and on the other 
hand, when Lucifer was seen in the morning, the bright evening star. Vesper, had disappeared. Accordingly, 
it came to be discovered that what had hitherto been called two separate stars were simply different appear- 
ances of one and the same planet. This planet was also named the " Shepherd's Star," but it is now better 
known by the name given to it by those who, recognising its superior brilliancy and beauty among the " host 
of heaven," called it after their most beautiful divinity — Venus. 

The brilliancy of this planet, as already mentioned, is such as to surpass all the other stars in the heavens. 
This being so, one would imagine that, of the eight orbs which circle round the central globe, this one would 
undoubtedly be among the largest. Such, however, is far from being the case ; Venus is a globe not quite so 
large as our earth. Her brilliant light, which makes her so conspicuous, is only borrowed ; as, like our own 
planet, she is a dark globe shining only by the light of the sun. 

As Venus revolves round the " central orb " in a path interior to the orbit of the earth, the year there will 
be much shorter than ours. In fact, the time occupied by this planet in making a complete revolution round 
the sun is scarcely 225 days, or about seven and a-half months. Her distance from the sun is about sixty- 
seven millions of miles, which is a little less than three-fourths of the distance which separates that luminary 
from our globe. The day there is also less than ours, being about twenty-three hours and twenty-one and 
a-half minutes, so that there are over 230 days in the year of Venus. As the axis of the planet is inclined to 
her path, there will take place there, as on earth, all that wonderful variety of the seasons. Her year, however, 
being shorter than ours, each season can last for scarcely two of our months. 

This beautiful planet, then, is in many respects a world such as ours. It has its year and its seasons. It 
rotates on its axis, and thus has days and nights, and it is a globe approaching very nearly ours in size — its 
diameter being only about 200 miles less than the diameter of the earth. It is, however, not quite so heavy 

43 



44 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



a globe as the earth, as the materials forming it arc somewhat lighter than those composing our world. In one 
respect Venus is greatly inferior to our globe, in the fact that she has no attendant planet or satellite. 

The heat of the sun on this planet must be excessive, for the solar heat is there twice stronger than on 
earth. It will, however, be considerably tempered by the dense clouds which float in the air surrounding the 
planet, as it has been found that Venus has even a more extensive atmosphere than our earth. The effects of 
this air surrounding the planet have been seen very plainly on several occasions. Like Mercury, Venus 
sometimes comes between us and the sun, at her inferior conjunction, and passes directly in front of the solar 
globe. When this takes place, the planet is seen to travel from left to right, as a black spot across the sun's 
bright disc. It was thus seen to move over, or to " transit," the solar disc in 1874, and again in 1882, but 
there will not be another till the year 2004, as will be seen from the Table. When Venus is just appearing to 
enter on the solar disc, a ring of brilliant light is seen surrounding that side of the planet which is farthest 
from the sun ; and the same phenomenon is again observed when part of the planet has passed off the sun's 
face. This ring of light is caused by the air surrounding the planet bending the solar rays towards the earth, 



TKANSITS OF VENUS. 



V A TE. 


REMARKS. 


1631. 
1639. 


December 7 
4 


Not observed 

Observed by Horrox and Crabtree 


!- at ascending node. 


1761. 
1769. 


June 5 
3 


Observed in various parts of the world 
)> » )> 


J- at descending node. 


1874. 
1882. 


December 9 
„ 6 


» !f J> 
1» ■ » ?J- 


j- at ascending node. 


2004. 
2012. 


June 8 
6 




I at descending node. 



and bringing them into view. Now, as this ring of light is exceedingly brilliant, it shows that there must be 
a large quantity of sunlight bent, or refracted, towards us, which again proves that the atmosphere of Venus 
must be very dense. This atmosphere, like Mercury's, contains large quantities of watery vapour, which implies 
the existence of large tracts of water on the globe of the planet. 

On the surface of Venus there have been detected very high mountains. Oceans and continents are also 
there, and very probably inhabitants. In fact, at present, Venus is probably the only inhabited planet in the 
solar system besides our earth. True, the heat of the sun must there be very scorching, but this may not be 
any drawback whatever to the existence of living creatures. On earth we find that all life is constituted for 
the position in which it is placed — whether that position be the barren and frozen regions surrounding our 
poles, or the scorching wastes near the equator. Accordingly, if life exists on Venus, it will, without 
doubt, be adapted to its surroundings. If some of these beings are intelligent, and capable of thinking like 
man, they cannot fail to notice, shining at night in their moonless skies, a brilliant star (our earth) with a small 
companion star (the moon) near it. From observations they will find that the small star revolves regularly 
round the large one; that the large star is like their own globe — a planet moving round the sun ; and while 
they gaze at it they will doubtless wonder if that distant orb, with its tiny companion, can be, like their world, 
the home of intelligent beings ; or if their globe alone, of all the " countless host of heaven," is the only abode 
of intelligent life. 



The Earth. 

" Like the baseless fabric of this vision, 
The great globe itself, 
Yea, all which it inlierits, shall dissolve." — Shakespeare. 

The earth is the largest of the inner planets, being nearly equal to the combined volumes of Mercury, Venus, 
and Mars. Her mean or average diameter is very nearly 791 8 miles in length, so that her surface contains 
no less than about 197 millions of square miles. In shape our planet is not truly globular, but slightly 
elliptical, the larger or equatorial diameter being about twenty-five miles longer than the diameter from pole 
to pole. Accordingly the polar diameter amounts to 7901'6 miles, and the diameter from opposite points of 
the equator to 7926'6 miles. Owing to this ellipsoidal form the degrees of latitude, which would be of 
the same length on every part of the earth if her form were spherical, increase in size as they recede from 
the equator. 

Length of a Degree of Latitude at different distances from the Equator. 
LATITUDE, 0° 10° 20° 30° 40° 50° 60° 70" 80^ 90° 

LENGTH OF A DEGREE IN MILES, 68-70 6872 68-78 68-83 6898 69-11 69-22 69-31 69-36 69-39 

As in volume, the terrestrial globe is also in total weight or mass about equal to the combined weights of 
the other members of the inner group of planets. From numerous observations of the attractive influence of 
the earth, it has been determined that this weight amounts to no less than 6,000,000,000,000,000,000,000 of 
tons. Accordingly the average density, or comparative weight, of the terrestrial material is about five and 
a-half times greater than that of water ; or it would require five and a-half globes the same size as ours 
composed of water, to equal the earth in weight. 

Like the other members of the planetary system the earth moves round the sun in a path that deviates 
slightly from a true circle (see Plate 11). As explained in Chapter VI., the sun does not occupy the centre of 
this elliptical curve, but one of the two points in it called the foci. The distance of our globe from the centre 
of her movement, is, in consequence, subject to a considerable variation. Iq fact, throughout an entire 
revolution this alteration of distance from the sun amounts to no less than about three millions of miles. At 
the beginning of January, for instance, when the earth is nearest to the sun, or in 'perihelion, the distance 
amounts to 91,336,000 miles ; while at the commencement of July, when our globe is in the opposite part of 
her orbit, or in aphelion, the distance is increased to 94,458,000 miles. The velocity of the earth in 
traversing her orbit, which, on the average, is about eighteen and a-half miles per second, is likemse subject 
to variation. Owing to the laws of gravitation, the nearer a heavenly body is to the governing mass, the 
greater becomes its orbital velocity. In the case of our globe this variation of speed throughout the year, 
from the ellipticity of the terrestrial orbit, amounts to over half-a-mile per second, or in the proportion 
of6lto59. 

The distance of the sun from the centre of the elliptical orbit of a planet, in proportion to the planet's 

mean distance from the central orb, or to the length of the semi-major axis of the path, is termed the 

eccentricity of the orbit— the amount of the sun's displacement from the centre. As already mentioned, the 

terrestrial orbit differs but slightly from a true circle, the eccentricity being about one-sixtieth (-0168) of the 

sun's average distance, or the sun is distant from the centre of her orbit 1,560,000 miles. As in the case of 

every other planet, the eccentricity of the earth's orbit is subject, throughout long periods, to a considerable 

variation. This change of ellipticity produces an alteration of the supply and distribution throughout the 

u 46 



46 



A FOFULAB HANDBOOK AND ATLAS OF ASTRONOMY. 



year of light and heat received from the sun, thus affecting the temperature and climates of our globe, and 
having in the past, in all probability, been the principal cause of the different glacial epochs. 



THE ECCENTRICITY OF THE TERRESTRIAL ORBIT FOR 200,000 YEARS. 



YEAR B.C. 


ECCENTRICITY 

{expressed as a fraction of 

the semi-major axis). 


LONGITUDE 
OF PERIHELION. 


YEAR A.D. 


ECCENTRICITY 

{expressed as a fraction of 

the semi-major a,xis). 


LONGITUDE 
OF PERIHELION. 


100,000 


0-0473 


316° 18' 





0-0168 


99° 30' 


90,000 


0-0452 


340° 2' 


10,000 


0-0115 


134° 14' 


80,000 


0-0398 


4° 13' 


20,000 


0-0047 


192° 22' 


70,000 


0-0316 


27° 22' 


30,000 


0-0059 


318° 47' 


60,000 


0-0218 


46° 8' 


40,000 


0-0124 


6° 25' 


50,000 


0-0131 


50° 14' 


50,000 


00173 


38° 3' 


40,000 


0-0109 


28° 36' 


60,000 


0-0199 


64° 31' 


30,000 


0-0151 


25° 50' 


70,000 


0-0211 


71° 7' 


20,000 


0-0188 


44° 0' 


80,000 


0-0188 


101° 38' 


10,000 


0-0187 


78° 28' 


90,000 


0-0176 


109° 19' 





0-0168 


99° 30' 


100,000 


0-0189 


114° 5' 



Th3 interval occupied by our globe in making a complete revolution of her orbit is termed the year. This 
is of different lengths, depending on the manner in which it is determined. If, for example, the interval 
observed be the one occupied by our globe in returning to the same part of her orbit with respect to a star, it 
is equal to the true period of the earth's revolution round the sun. This period is called a Sidereal Year, or 
year determined from the stars, whose length is 365 days 6 hours 9 minutes 9 seconds. While, however, this 
is the only true year, it is not, as might have been supposed, the one that is employed chronologically. The 
calendar being arranged according to the seasons, and as these entirely depend on the position of the sun, the 
Solar, or Tropical Year is the one generally used. It is about twenty minutes shorter than the sidereal year. 
Owing to the swaying of the earth's axis, or the precession of the equinoxes, the return of the sun to the same 
tropic, or to the equator, takes place sooner than the interval occupied by our globe in making a complete 
orbital revolution. Accordingly the tropical year is only 365 days 5 hours 48 minutes 46 seconds in length. 
But there is yet a third year, one determined by the return of the earth to the same part of her path. If the 
orbit of our globe were stationary this latter year would be of exactly the same length as the sidereal year. 
The axes of the orbit, however, as will be seen from the above Table containing the position of the perihelion 
for different epochs, are not fixed, they, on the contrary, slowly move round the sun towards the east, or in the 
same direction as that in which the earth journeys, and complete a revolution in about 108 thousand years. 
From this movement the earth, before returning to the same part of her path, has to accomplish more than a 
complete period of revolution, as during the interval the point on the orbit has moved forward in the same 
direction as our globe. The interval, therefore, between two successive returns to the same part of the orbit 
(the perihelion, or aphelion, for instance) is longer than even a sidereal year. It is called the Anomalistic 
Year, and is 365 days 6 hours 13 minutes 48 seconds in length. 

Besides travelling round the sun once in a year, our globe has also a movement, or rotation, round its axis 
once every 23 hours 56 minutes 4 seconds. This period is termed a Sidereal Day, because in exactly this 



TRE PLANETARY SYSTEM. 



47 



interval the stars, which are apparently fixed on the celestial sphere, return to the same positions with respect 
to the horizon of the observer. As the earth, however, is not at rest, but rapidly revolving round the great 
centre of the planetary system, the sun is apparently caused to move among the stars in an easterly direction, 
and is thus on the average about four minutes longer than a sidereal day in returning to the meridian. The 
mean Solar Day is accordingly 24 hours in length, while the actual or apparent day alters slightly throughout 
the year. This is owing to the varying speed of our globe in her orbit, which lengthens or shortens the 
observed interval between the successive returns of the sun to the meridian, or the true solar day. 

The axis round which the earth performs her rotation is greatly inclined to the plane of the path in which 
she moves. At present it is inclined at an angle of 23 degrees 27 minutes from a vertical to the plane of the 
ecliptic, and this is also the angle between the terrestrial equator and the ecliptic. Like the eccentricity of 
the orbit, this inclination, which is called the obliquity of the ecliptic, is subject to a slight alteration. During 
the last two thousand years it has decreased to the extent of about twenty-four minutes, and is still decreasing 
at the rate of about half a second of arc each year. It is computed that the diminution Avill continue for about 
fifteen thousand years, when the obliquity will be reduced to about 22^ degrees. The direction of movement 
will then change, and the axis of our globe will begin to recede from a vertical to the orbit, or from the poles 
of the ecliptic, and the obliquity will accordingly increase. It is believed, however, that the whole variation 
can never exceed two and a half degrees, so that the seasons, which entirely depend on the inclination of the 
axis, can never seriously be altered. 



THE OBSERVED OBLIQUITY OF THE ECLIPTIC FOR NEARLY 3000 YEARS. 



DATE. 


OBSERVER. 


OBLIQUITY, on 

INCLINATION OF THE 

EQUATOR TO THE 

ECLIPTIC. 


DATE. 


OBSERVER. 


OBLIQUITY, OR 

INCLINATION OF THE 

EQUATOR TO THE 

ECLIPTIC. 


1100 


B.C. 


Tclicon-Kong (China). 


23° 54' 2" 


1690 


A.D. 


Flamsteed at Greenwich. 


23° 28' 48" 


350 


)) 


Pytheas at Marseilles. 


23° 49' 20" 


1750 




Lacialle. 


23° 28' 19" 


200 


5) 


Eratosthenes. 


23° 51' 15" 


1755 




Bradley at Greenwich. 


23° 28' 15" 


140 


!) 


Hipparchus. 


23° 51' 20" 


1769 




Maskelyne. 


23° 28' 10" 


827 


A.D. 


Arabians at Baghdad. 


23° 33' 52" 


1800 




Do. 


23° 27' 57" 


890 


>> 


Albategni at Antioch. 


23° 35' 41" 


1815 




Bessel. 


23° 27' 47" 


1150 


)) 


Almansor. 


23° 33' 30" 


1825 




Pearson. 


23° 27' 44" 


1278 


)) 


The Chinese. 


23° 32' 12" 


1841 




Bouvard at Paris. 


23° 27' 35" 


1430 


>J 


Ulugh Begh (Samarkand). 


23° 31' 58" 


1868 




Airy at Greenwich. 


23° 27' 22" 


1590 


jj 


Tycho Brahe. 


23° 29' 52" 


1890 




(Nautical Almanac). 


23° 27' 13" 


1672 


)) 


Cassini at Bologna. 


23° 29' 15" 











Mars. 

" Each sun with, the worlds that round it roll, 
Each planet poised on her turning pole, 
With her isles of green, and her clouds of white, 
And her waters that lie like fluid light." — Bryant. 

We now come to the outermost member of the inner group of orbs — the planet Mars — the least of all the 
major planets, with the exception of Mercury. Mars revolves round the sun at an average distance of 141| 
millions of miles, in a path very elliptical in shape (see Plate 11). In fact, the eccentricity of his orbit 
is, after Mercury's, greater than in the case of any other large planet. It amounts to about one-eleventh 
(0'093) of the semi-major axis of the orbit. The distance of the planet is consequently subject to great varia- 
tion. When nearest to the sun, the distance amounts to nearly 128 millions of miles, and when at his farthest 
from the centre of the system, to over 155 millions of miles. The time occupied by the planet in making a 
circuit of this orbit is nearly twice greater than in the case of our earth. More exactly, it is equal to 1 year 
10| months; this gives an average orbital velocity of about 15 miles per second. 

From being situated immediately outside the terrestrial orbit, the distance of the planet from the earth 
varies to an enormous extent. When in opposition to the sun, for example, or when seen near the meridian 
at midnight, Mars is then nearer to our globe than when in the opposite part of the heavens, or in conjunction 
with the sun, by a whole diameter of the martial orbit, 'minus the difference between the distances of the 
planet and the earth from the sun, or by no less than 234 millions of miles.* The distance between the two 
planets, when Mars is in opposition to the sun, or when they are in conjunction with each other, amounts to 
nearly 49 millions of miles. This is the average distance, however, for the planet is sometimes nearer, and 
occasionally further away than this when in opposition. As already mentioned, the distance of the planet 
from the sun varies to the extent of about 26 millions of miles, which, is also the amount by which the opposi- 
tion distances alter. If the planet, accordingly, happens to be near the aphelion of its orbit, or at its greatest 
distance from the sun, when in conjunction with our globe, the least distance between the two planets is then 
greatest, and amounts to 61 millions of miles. If, on the other hand, the opposition occurs when the planet 
is in perihelion, the distance is then the shortest possible, being only 35 millions of miles. As might be 
expected, this great variation of the planet's distance when in opposition produces a considerable alteration in 
its brilliancy, and in the apparent size of its diameter. But this variation of brightness is even more marked 
than it would be solely from an increase or decrease of distance between the two bodies. When Mars is 
nearest to the earth, he is then nearest to the sun, and, therefore, his disc is more brilliantly illuminated than 
when situated at his mean distance. Accordingly, the difference between the brilliancy of the planet when 
nearest to us at opposition, and whea farthest away, is as great as five to one — i.e., Mars, when seen in peri- 
helion opposition, is five times brighter than when seen in aphelion opposition. 

In size or volume the globe of the planet is about one-seventh of the volume of the terrestrial globe, its 
diameter being 4200 miles. The surface, therefore, amounts to about 55 millions of square miles, or is about 
equal to one-fourth of the earth's surface. The material of which the planet is formed is considerably lighter 
than the terrestrial material, its average density being only about seven-tenths of the density of the matter 
composing our globe ; for, instead of being one-seventh of the mass of the earth, it is scarcely one-ninth of 
the terrestrial mass. The attraction of superficial gravity on the planet, or the force with which all objects 
are drawn towards the centre of the martial sphere, is also much less than on our globe. In fact, it is only 

* =283,000,000 (the mean diameter of the orbit) - 48,700,000 (the difference between the distance of Mars and the earth), 
--234,300,000 miles. 

48 



I 



THE PLANETARY SYSTEM. 49 



about one-third of the attraction on the surface of the earth, or as 38 to 100 ; so that a body which weighs 100 
pounds here, would, if removed to Mars, weigh only 38 pounds. 

Like the other members of the planetary system. Mars turns on his axis, making a complete rotation in 
24 hours 37 minutes 227 seconds. This rotation period is known more accurately than that of any other 
planet, as it has been determined by observations of permanent markings on his surface, extending over 
two hundred years. The axis of rotation is, in the same manner as the axis of our globe, inclined slightly 
from a vertical to the plane in which the planet moves. This angle of inclination from the vertical, or 
between the planet's equator and the plane of its path, amounts to 24 degrees 50 minutes, which, it will 
be noticed, differs but slightly from the obliquity of the ecliptic. Accordingly, the Martial seasons which 
depend on this circumstance are much the same as our own, only they are of about twice the length, as 
each season on Mars lasts nearly five and a-half months. 

To the telescopist Mars is the most interesting of the planets, as in appearance he approaches nearer to 
the earth than any other member of the planetary system. When viewed with a powerful instrument, the 
planet's disc is found to be covered with numerous delicately-tinted markings. These are of two distinct 
shades. The darker tints have a decidedly greenish hue, and the brighter parts a yellowish-red colour. The 
nature of these markings has long been known. The greenish portions of the disc are found to be large tracts 
of water, or oceans ; and the ruddy parts land, or continents. This configuration of land and water on the 
surface of the planet has, from numerous observations of Mars made with the most powerful instruments on 
all parts of the earth, been very accurately delineated ; and even a chart of the whole surface has been con- 
structed. Such a chart, constructed from the most recent observations, is given in Plate 12. From this map 
it will be noticed that, as in the case of our earth, the southern hemisphere of the planet contains more water 
than the northern hemisphere. The winters there also appear to be more severe than in the opposite hemi- 
sphere, as the southern pole is covered with ice and snow to a wider extent than the northern pole. This 
difference of climate between the two hemispheres is believed to be chiefly owing to the present position of 
the planet's axis, a position which gives the winter to the southern hemisphere, at the time the planet is 
farthest from the sun. The ice-caps surrounding the poles of Mars are very conspicuous objects, and were 
among the first markings discovered on the surface of the planet (see Plate 15). Before the spectroscope was 
invented, it was almost impossible to know exactly of what the brilliant white markings near the poles were 
composed. Telescopic observation alone, however, did much to reveal their true nature. Careful scrutiny 
soon found that the polar cap, which, from the motion of the planet in its orbit, was being more and more 
directed to the sun, gradually diminished, while on the other hand the cap surrounding the opposite pole 
slowly increased as a consequence of the presence and withdrawal, from the alteration of the seasons, of the 
solar rays on the masses of polar snow and ice. 

Within the last forty years several portions of the oceans of the planet have been found to have altered 
slightly in shape. In some instances it has been observed that hundreds of square miles of land have become 
covered with water, and as large portions of the seas have become dry. Most probably these changes have 
been produced by inundation, and also by an alteration of the surface level of parts of the planet's 
globe. This would be accomplished all the easier as the land in those parts where the changes have been 
detected is exceedingly flat and of about the same level as the surface of the water. In fact, nearly all the 
martial continents lie at rather a low level ; as Mars is a planet not nearly so mountainous as Mercury or 
our earth. Like the other members of the planetary system. Mars is surrounded with an atmosphere, and as 
there is water on his surface, evaporation will raise quantities of it, and clouds will be formed as on our globe. 
Indeed, clouds have not unfrequently been observed floating in the martial atmosphere, so that on Mars there 
undoubtedly takes place all the phenomena of rain, hail, and snow. 

Mars, like Venus, may not improbably be the abode of some form of life. If life, however, exists there, 
it will of necessity be greatly different from the varied forms we see on earth ; as the conditions for the exist- 



50 A POJPULAB HANDBOOK AND ATLAS OF ASTRONOMY. 



ence of life on a planet depend entirely on the planet's position, volume, density, and physical constitution. 
Mars, we have found, is more distant from the sun than the earth, consequently his supply of light and heat is 
considerably less than the terrestrial supply, being, indeed, scarcely one-half of the amount which the earth 
receives. This fact, however, cannot be taken as an exact index of the temperature of the martial surface. 
The temperature of a planet's surface certainly depends in a great measure on the distance of the planet from 
the sun, but it is considerably modified by the presence of an atmosphere. Mars, we know, has an atmo- 
sphere surrounding him, and an atmosphere, too, containing large quantities of watery vapour, which greatly 
increases its heat-retaining power, so that Mars is probably not so cold a planet as many have supposed. 
The mildness of the martial climates is also proved from the fact that the water on the surface of the planet is 
frozen only near the poles, and even there the cold is not so great as in our arctic and antarctic regions. The 
planet's snow-caps are also not nearly so extensive as those of our earth. But even though it were proved 
that the conditions of the surface of the planet were such that no terrestrial life could exist there, this does 
not by any means imply that there is no martial life whatever. We must not for a moment imagine that the 
forms of life found on our globe are the only possible ones ; that, in short, the different orbs of the universe are 
exact representations of our sun, and the planets revolving round those orbs, and round our sun, are true copies 
of our globe. Modern scientific discovery has for ever dispelled such an absurd supposition. Accordingly 
there is some reason for believing that Mars may be the abode of intelligent life, or if not at present, may 
have been in the past an inhabited world. 

Till the year 1877 it was believed that Mars, like Venus and Mercury, had no satellite. Times without 
number the planet was examined with the most powerful telescopes, but all observers failed in turn. In 
the month of August, 1877, however, Professor Hall at Washington, with a new refracting telescope of 
twenty-six inches aperture, discovered that the planet had two moons revolving round him. They are 
exceedingly minute globes, thought to be less than ten miles in diameter, and can only be seen with the 
largest instruments, and only with these when Mars is nearest to the earth at the time of opposition. The 
outer one, Demois, is situated from the centre of the planet at a distance of 14,C00 miles {see Plate 14). Its 
period of revolution is exceedingly short, being only 30 hours 18 minutes in length ; in which time it will 
undergo all its phases. Phobos, the inner satellite, is distant 5,800 miles from the centre of Mars, and 3,700 
miles from his surface. Unlike any other satellite in the solar system, the time occupied by it in making a 
complete revolution of its orbit is considerably shorter than the period of the planet's rotation. The revolu- 
tion is completed, in fact, in less than one-third of the martial day, or in 7 hours 39 minutes. From these 
rapid revolutions of the satellites, there results the most striking pecularity. Phobos, the inner one, for 
instance, will appear to rise in the western part of the sky and set in the east, notwithstanding the fact that 
its direction of revolution is the same as in the case of our own moon, or from west to east. The interval 
between rising and setting, however, will be lengthened from the planet's rotation, and in consequence a 
complete change of phases will be accomplished while above the horizon. As seen from the surface of Mars 
the apparent movement of the outer satellite will be just as peculiar. Its period of revolution, we have seen, 
coincides more closely with the rotation period of the planet, than that of the inner moon, and consequently 
its apparent movement in the sky, or with respect to the horizon, will be exceedingly slow, while its sidereal 
movement, or its motion among the stars, will be as rapid as the angular movement in its orbit. Like our own 
moon, Demois will rise in the east and set in the west, but from the slowness of its apparent movement in the 
sky, the interval between rising and setting will be lengthened to no less than 132 hours, in which time four 
complete changes of phases, or four orbital revolutions, will actually be accomplished. 



Chart of Mars — Plate 12. 



CO 

< 



z 

< 

w 

X 

o 

CC 
< 

X 




/ 




~ 


/ 

/ 


-J- 


r 

r 


r 


.^^ 


1 ^ 




\ 



The Asteroids. 

Towards the end of last century, and before Neptune had been discovered, it was thought that the different 
planets were, according to some definite law, placed at certain distances from the sun. It was known, for 
instance, that if the various orbs from Mercury to Uranus were represented by the geometrical series, 
0, 3, 6, 12, 24, &c., and each number of the series further increased by 4 (as in the following Table), the 
numbers thus obtained approximately represented the distances of the different planets from the sun. But 



PLANETS. 


Mercdky. 


Venus. 


The Earth. 


Mars. 


Missing 
Planet. 


Jupiter. 


Saturn. 


Uranus. 


Geometrical Series 
+ 4 

Eesulting Distances 
Actual Distances 




4 


3 

4 


6 

4 


12 

4 


24 
4 


48 
4 


96 

4 


192 

4 


4 
3-9 


7 
7-2 


10 
10 


16 
15-2 


28 


52 
52 


100 
95-4 


196 
191-8 



while this was found to be the case it was noticed that before this regularity of arrangement of distance could 
be considered as complete, a planet ought to revolve in a place where hitherto no planet was known to exist — 
viz., between the orbits of Mars and Jupiter. Astronomers, accordingly, began the search for the supposed 
orb, which, if it existed, could not be a very large one, or it would have already been discovered. Their 
labours were soon rewarded, for on the very first day of the present century, Piazzi, at Palermo, discovered the 
small planet Ceres, which, curiously enough, was found to be revolving exactly at the distance which had been 
assigned to it. But this was not all. Two years after this remarkable discovery, on the 28th of March, 1802, 
another small planet, which was called Pallas, was discovered by Olbers at Bremen. These discoveries were 
soon followed by two others — viz., the small planet Juno, on the 1st of September, 1804, and Vesta, on 29th 
March, 1807. No additional asteroid, however, was discovered for thirty-eight years, but since the year 1845, 
there has scarcely been a year without their number being greatly increased, till at present nearly three 
hundred of these small planets have been discovered. These, however, do not represent their actual numbers, 
which very probably can only be reckoned by millions. 

The paths in which these tiny orbs revolve are situated at different distances from the sun, and at various 

inclinations to the plane of the ecliptic {see Plate 13). The one known as Medusa (lo) has the least 

mean distance, or 198 millions of miles, and has consequently the shortest period of revolution — viz., 

3 years 40 days. Hilda (i53 j on the other hand, is the most distant member of the group as at present 

known. Its average distance from the sun is 366 millions of miles, and its period of revolution is accordingly 
nearly eight years. The asteroids thus form a ring of tiny orbs, revolving between the paths of Mars and 
Jupiter, whose breadth is no less than 168 millions of miles, or nearly equal to the diameter of the terrestrial 
orbit. The paths of these small orbs do not, in general, deviate far from the ecliptic plane, being on the 
average inclined to the plane of the earth's orbit at an angle of about six degrees. Several, however, have 
orbits inclined at an angle considerably greater than this. The orbit of Pallas, for instance, has an inclina- 
tion of no less than thirty -five degrees (see Plate 13). 

In si?e the asteroids may be considered as the smallest bodies of the planetary system. The largest even 



52 A FOPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



(Yesta) is believed to have a diameter of only three hundred miles. The remaining three of the four first 
discovered have probably diameters no greater than two hundred miles ; while many of the others cannot have 
diameters larger than fifty miles, the vast majority of them being globes, in all likelihood, as small as ten or 
twenty miles in diameter. With regard to their mass very little is knoAvn, but from the irregularities of 
the movements of Mars it has been calculated that the combined masses of all the asteroids cannot be 
greater than one-fourth of the mass of our globe, and would, if put together, only form a sphere with a 
diameter of about 5000 miles. This clearly proves that even the largest asteroid can neither be a very large 
nor heavy globe. Most probably it would be only one twenty-thousandth of the weight of the earth ; while the 
smallest may be no heavier than one of those huge projectiles, which are occasionally fired from the largest 
pieces of ordnance. 

The origin of these asteriods is probably the outcome of the condensation of a mighty ring of nebulous 
material, which, instead of breaking up and forming large globes, as in the case of the other planets, condensed 
into numerous smaller ones. This would doubtless be owing to the attractions of the large planet revolving 
immediately outside their paths — viz., Jupiter, the giant of the sj^stem. Their production, certainly, cannot 
be accidental, as some have supposed, but the outcome of a definite law. The peculiar position they 
occupy in the system very well proves this, for they divide the larger planets into two important groups — the 
inner members from the outer — the terrestrial planets from the giant planets. 




Omamoj'A iy V.I'cA. 



The Solar System — Plate 13. 




£>u>Ti>«< .S f-tiihAlJ *■ f-J* JUut' 



J U P I T E E. 

" Flowers of the sky ! ye, too. to age must yield, 
Frail as your silken sisters of the field." — Erasmus Darwin. 

As already mentioned, this is the nearest member of the outer group of orbs, and the largest planet in the 
system. On the average, this giant planet is situated from the sun at a distance of 483 millions of miles. As 
the eccentricity of the orbit, however, amounts to about one-twentieth of the semi-major axis (O'OIS) his 
distance from the sun varies to the extent of about 42 millions of miles. In traversing this laro-e orbit the 
planet journeys at the velocity of slightly over eight miles per second, and accordingly occupies nearly twelve 
years, or 4332'6 days, in making a complete revolution. In size and weight Jupiter far exceeds any other 
member of the planetary system, being, in fact, larger and heavier than all the other planets put together. 
The equatorial diameter of this large globe is no less than 88,200 miles — thus exceeding the diameter of the 
earth, as much as the diameter of the sun exceeds that of Jupiter itself The shape of this huge planet is 
very elliptical, and his ellipticity is such as to be clearly perceptible when viewed with the telescope. Owinc 
to this ellipticity the polar diameter is about one-seventeenth, or actually 5000 miles less than the equatorial 
diameter, and is therefore equal to 83,000 miles. From this large diameter it follows that the surface of the 
planet is 119 times, and the volume 1300 times larger than those of the earth. But though Jupiter is so 
many times larger than our globe, he is only about 316 times heavier, which proves that the matter composing 
the globe of the planet must be considerably lighter than that which forms our earth. In fact, this gigantic 
planet is but little heavier than if he were composed entirely of water — his density being scarcely one-fourth 
of the earth's, and exactly the same as that of the sun. The amount, however, of this very light material is 
so great that, notwithstanding the distance of his visible surface from his centre, the attraction of gravity 
there will be nearly three times greater than it is on the surface of our globe. This, however, is taking the 
visible surface as representing the real surface of the planet. In all probability the actual surface is consider- 
ably smaller, for the planet is surrounded with an exceedingly dense atmosphere, which is certainly several 
thousands of miles in depth. Therefore, on the true surface of Jupiter's globe, the attraction will be very 
much greater than what we have been considering as the amount on the visible surface. 

When examined with a telescope, the disc of Jupiter is seen to be crossed with several delicately- 
coloured bands, and it is from observations of these bands that the rotation period has been determined. 
This period, notwithstanding the gigantic size of the planet, is very short, being only about 9 hours 
55 minutes. Sometimes the belts, as the coloured bands are called, are of a pale bluish colour, while 
occasionally portions of them have a red appearance. These markings are entirely atmospheric, being 
simply large cloud masses, which are continually shifting in position, and altering in shape, even while 
they are being viewed (see Plate 15). They are arranged in strips parallel to the planet's equator, 
doubtless resulting from his rapid rotation, which will produce winds blowing constantly in one direction, 
or similar to our trade winds on earth. These winds, too, must occasionally blow with more than 
hurricane force, judging from the rapidity with which the cloud-zones sometimes change their form. 
Indeed, clouds in the atmosphere of Jupiter have actually been observed to travel over a distance of 
two hundred miles in so short an interval as an hour. This shows that the surface of the planet 
must be subjected to atmospheric storms more tremendous than are ever experienced on earth. These 
Jovian hurricanes that are continually raging owe their existence to the planet's internal heat ; for, 
thousands of miles below the visible surface, there is situated the red-hot fiery nucleus, part of which 
is occasionally seen whenever a portion of one of the great cloud-zones is for a time dispersed. 

It would seem, then, that at present this gigantic planet cannot be the abode of life. For, independent 
of the internal heat, the storms on his surface are such that no forms of life known to us could ever 

H 53 



54 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



survive their effect. It is rather a planet in preparation for life, in a condition similar to that in which 
our earth was many millions of years ago, when no life whatever could have existed on her surface — 
at a time, in our world's history, so very remote that geology can only infer its existence. This reveals 
the enormous length of the periods of time that are required for a planet to condense and cool from 
the molten state, and become fit for the abode of living creatures; and it also reveals that the entire 
duration of life on a planet is infinitely short in comparison with the planet's existence. 

Jupiter has no less than four satellites, which were the first heavenly bodies discovered with the 
telescope. They revolve round him at distances ranging from 262,000 to over one million of miles, 
and in periods varying from 1 day 18i hours to 16 days 16-|- hours (see Plate 14, also Table at end 
of chapter). The paths in which they move are nearly circular in shape, and coincide with the plane 
of the planet's equator. The largest of these moons, Ganymede, has a diameter approaching Mercury's, 
or about one-half that of the earth, being no less than 3600 miles. The diameter of the next largest 
is 3000 miles, while the other two are globes of about the same size as our own moon, with diameters 
of slightly over 2000 miles. Though they are so large, they are formed of very light material, lighter 
even than that composing the globe of Jupiter, for they are each about the same Aveight as if formed 
of cork. Owing to their orbits being situated nearly in the plane of Jupiter's orbit, which does not 
differ greatly from the plane of his equator, the satellites, with the exception of the most distant one, 
pass through Jupiter's shadow, and are eclipsed at every revolution ; and it was from observations of 
these eclipses that the Danish astronomer Roemer, in the year 1675, discovered that light occupied 
time in journeying over a given distance. More modern observations show that the eclipses of all the 
satellites take place 16 minutes later, when the planet is in conjunction with the sun, or when furthest 
from the earth, than when in opposition, or nearest to our globe, which is the time occupied by light 
in travelling from one side to the other of the terrestrial orbit. 



I 



The Orbits of the Satellites — Plate 14. 



INCUNATIONS 

of the OAlls of 

Sa^tartifi Satellites 




INrUNATlON 
of tile Luuor Orbit 



. INlUNAIION 
of ik-OrUlaof 



En^ra^cd. by Ai-nhihalcLi.J'ecK.Jiain'. 



S A T U H K. 

"In the deep stillness of tlie night, 
When weary labour is at rest, 
How lovely is the scene ! " — Miller. 

To those who are familiar with the more important of the star groups, the movements of this planet 
round the heavens will be watched with special interest. For many centuries, the movements of this 
and similar orbs have constantly been observed. In fact, thousands of years before our era, the shepherd 
astronomers in the extensive plains of Chaldea or Central Asia had — 

" Watched, from the centres of their sleeping flocks, 
Those radiant Mercuries that seemed to move," 

and discovered that while nearly all the starry host seemed stationary with regard to each other, though 
appearing, of course, to turn daily round the sky, yet at least four orbs were constantly changing their 
positions. By these early astronomers the movements of the Avandering stars were carefully watched, 
and their tracks among the constellations recorded. By this means it was found that these orbs did 
not all move with the same velocity. Some appeared to travel very rapidly, while others were observed 
to move with great slowness. The fastest moving orb, which we now call Venus, was the most brilliant; 
the slowest moving one, Saturn, the least conspicuous. From his sluggish movements and dull appearance, 
the alchemists of old likened him to the heavy and lustreless metal, lead; while the astrologer selected 
him as a fit orb for producing the most mischievous influences on the human race. 

How vastly different all this is from the reality! "Truth," it has been well said, "is stranger than 
fiction." Modern science shows that the apparently insignificant is often the most wonderful, and, in doing 
this, it teaches us a valuable lesson— a lesson which we should not be slow to learn— viz., that we ought not 
to judge quickly as to the ways and works of tlje Creator ; not to say that this and that is the manner in 
which a particular object has been created, but rather, with patience, to search constantly after those great and 
sublime truths about the universe which are being slowly unfolded around us every day. To no object can this 
caution apply more than to Saturn. That dull orb, which so sluggishly appears to drag its course from 
constellation to constellation, is actually rushing through space at a speed which is more than twenty times 
that of a cannon ball, or six miles per second, and makes a complete circuit of its mighty path round the 
sun in about 29^ years. The average distance of the planet from the sun is about 886 millions of miles, or 
nearly ten times greater than the distance of our earth. Yet this vast orbit — whose span thus amounts to 
1800 millions of miles, over which light requires two hours and three-quarters to journey — is in turn 
insignificant when compared with the paths of the two large planets Uranus and Neptune, which have 
been discovered to revolve far beyond. 

Let us now turn that most useful instrument, the telescope, upon this apparently insignificant object. 
When this is done on some calm and clear evening, the picture presented to our eyes is magnificent. 
What, to the unaided eye, seems to be only an ordinary and not particularly brilliant star, appears under a 
high magnifying power, to be one of the most beautiful objects in the heavens — a glorious orb, whose shining 
surface is resplendent with the most delicately-coloured tints, and which is surrounded with a wonderful and 
complicated system of revolving rings (see Plate 15). 

Of the eight large globes which form the sun's planetary family, SATURN is by far the most wonderful. 

Second only in size to the giant planet Jupiter, he is himself a gigantic orb. The diameter of his mighty 

globe is no less than 75,000 miles, or over nine times greater than the diameter of the earth. Like our 

globe, his true shape is not exactly spherical; the polar diameter is nearly 7000 miles shorter than a 

S5 



56 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



diameter passing throngli his equator. The diameter of the planet being so large, his volume is in 
consequence 740 times greater than the volume of the earth; or, in other words, it would require 700 
globes, equal to ours in size, to form a globe the size of Saturn. This huge ball rotates in the 
same manner as our ea.rth, but much more rapidly ; for instead of taking twenty-four hours, as our earth 
does, to make a complete revolution, Saturn rotates on his axis in a little over ten hours. Owing to this 
rapid rotation, the equatorial regions of the planet are carried round at a tremendous velocity — a velocity 
nearly similar to that with which SATURN is carried round the sun — of about six miles j)er second. 

In mass, or the amount of matter which he contains, SATURN does not exceed our earth in the same pro- 
portion as he does in volume ; his bulk being only about one hundred times greater than that of our globe. 
Accordingly, while it would take 700 globes, equal to ours in size, to form a globe as large as 
Saturn's, it would only require ninety-five earths to form a globe equal to Saturn in weight. Now, as the 
planet is much larger, in proportion to its weight, than our earth, it follows that the materials of which he is 
built up, must be very much lighter than those forming our globe. In fact, the matter composing the gigantic 
globe of Saturn is so light, that if the planet could be placed in some mighty ocean, it would actually float 
with about one-fourth of its bulk above the surface of the water. 

In all probability SATURN is composed of materials similar to those of our globe. How is it then that they 
are so light comparatively ? The pressure on the central parts of the planet must be enormous — quite 
sufficient, indeed, to form matter of great density. Yet Ave find that the whole globe is so light that it would 
float in water ! The cause of this is to be found in the fact that the planet is exceedingly hot. This prevents 
even the great pressure of the central parts from forming any solid material ; so that at present the mass of 
the planet is simply expanded by heat. What we see in the telescope is not the real surface of Saturn, but 
his cloud-laden atmosphere ; far below which, there exists his glowing central ball. By the planet's rapid 
rotation, as in the case of Jupiter, these cloud-layers are thrown into numerous concentric zones, or "belts" 
(see Plate 15), which, when the air is exceedingly clear, are seen to be beautifully coloured. The general 
surface of the planet has a yellow appearance. Near the poles the colour is somewhat blue, while the 
equatorial belts are of a bright cream-coloured tint, and often contain brown, red, and purple spots. 

The most wonderful part of the planet, however, is his peculiar appendage. The breadth of this marvel- 
lous ring system is no less than twenty-one times greater than the diameter of the earth, yet it is so amazingly 
thin, that when placed exactly edgeways to us, it often disappears from view, and Saturn is then seen like any of 
the other planets — ringless. The bright ring, it will be noticed, is divided into two parts by a dark strip, called 
after its discoverer, " Cassini's division." This dark strip is nearly 2000 miles in breadth. Each of the two rings 
thus formed is in all probability broken up into numerous smaller rings. In 1856, it was discovered by means of 
one of the large American telescopes that Avithin the large bright ring there is a dark and semi-transparent ring 
about 10,000 miles broad. This discovery AA'as of the greatest importance, for it threw considerable light on 
the nature of the Avhole ring system. Before the telescope Avas poAverful enough to reveal its complicated 
structure, and before mathematical analysis had demonstrated its nature, the ring was thought to be solid. 
The discovery of the " crape ring," however, shoAved that this was impossible, which confirmed the statements 
of mathematicians that no solid ring could exist, as the attractive poAver of the planet would have broken it 
in pieces. Neither, it Avas reasoned, could the rings be of the nature of a fluid. In fact, the Avonderful system 
of rings AA'ith Avhich Saturn is engirdled, is now knoAvn to consist of nothing more than multitudes of tiny 
orbs^small moons, or " pocket planets " — each revolving round Saturn in its OAvn path, obeying as rigidly 
the great law of the universe, as our earth, or any of the larger members of the solar system. 

Outside the rings, there rcA^olve eight large satellites, or moons (see Plate 14). The smallest of these is 
thought to have a diameter about one-half that of our moon ; Avhile the largest is undoubtedly as large as the 
small planet Mercury. As the outermost of these satellites journeys round Saturn at a distance of two and a- 
quarter millions of miles, the span of his entire system thus amounts to about four and a-half millions of miles 



Plate 15. 




THJS PLANETARY SYSTEM. 57 



— a breadth which is nearly twenty times greater than the distance which separates our moon from the 
earth. 

At present, we have seen, Saturn is in a condition far too hot to be the abode of life. Yet though this is 
certainly the case, his heat may be of the greatest consequence to several of his satellites. At this enormous 
distance the heat of Saturn cannot, of course, be in the slightest degree sensible to us ; yet for all that, it mil 
be felt over his Avhole system — Saturn being to bis moons as a subordinate sun, swaying them by his force, and 
supplying them with his heat. And in the future, long after the various forms of life on our globe shall have 
ceased to exist ; when the water and atmosphere shall have been withdrawn into the interior ; and when, in 
short, our earth shall have become like the moon at present — a desolate waste — Saturn will then have cooled 
down, and probably become a fit abode for living creatures. Saturn is thus a unique orb — an orb which 
shows us, that even among the various members of the sun's family of planets, there exists the most wonderful 
variety, as everywhere throughout the whole universe. 



DIMENSIONS OF SATURN'S EINGS. 



Diameter of Outer Eing, . 


. 173,000 


miles. 


Diameter of Cassini's Division, 


. 148,000 


n 


Diameter of Middle Ring, . 


. 112,000 


n 


Diameter of Crape Ring, . 


. 91,000 


n 


Width of Bright Rings, , 


. 30,500 


» 



Distance between Crape or Gauze Ring and 

Surface of the Planet, . . 9,000 miles. 

Breadth of Cassini's Division, . . 2,000 „ 

Thickness of Ring, Probably less than 100 „ 



Ueanus. 



"Each planet shining in his proper sphere, 
Doth with just speed his radiant voyage steer." — Prior. 

This was the first planet discovered with the telescope, all the others interior to its orbit being visible to the 
unaided eye, and consequently known from very ancient times. The planet was first noticed to be a member 
of the solar system more than one hundred years ago — viz., on the 13th of March, 1781, though it had frequently 
been observed as a star on former occasions. On the evening of that day the elder Herschel, while examining 
the stars in the constellation of Gemini, detected an object which did not appear as an ordinary star. In a 
short time, from careful watching, he found that the strange star was moving, and announced that he had 
discovered a comet. Repeated observations, however, soon proved that the new star could not be a comet, as 
it was travelling round the sun in an orbit nearly circular, but was, instead, a planet moving in a path at more 
than twice the distance of Saturn. Since its discovery Uranus has made more than a complete revolution of 
its orbit, having travelled from the constellation of Gemini right round the zodiac, through Gemini again to 
the constellation of Virgo, where it is at present situated. Accordingly the period of the planet's orbital 
revolution is very accurately known, and from this its distance from the sun.* This period is slightly over 
eighty-four years, and consequently the distance from the sun will be over nineteen times greater than that of 
the earth, or about 1 800 millions of miles, from which it follows that the planet moves in its path at a velocity 
of over four miles per second. 

In size Uranus is slightly less than Neptune, and is therefore the smallest member of the outer group 
of planets. The diameter of his globe amounts to about 32,000 miles, hence the surface is sixteen times, and 
the volume about sixty-six times, greater respectively than those of our earth. The density of the planet is 
very small, being about the same as that of Jupiter, and greater than the density of Saturn or Neptune. The 
planet is thus but slightly heavier than if he were formed of water; and notwithstanding his gigantic size, his 
mass is only fifteen times greater than the mass of our globe. In shape, Uranus is not perfectly spherical, 
but like all the large planets, considerably compressed at the poles, the polar diameter being about one-four- 
teenth less than the equatorial diameter. It has recently been discovered that the planet's disc is crossed, like 
Jupiter's and Saturn's, by several faint bands, which implies that Uranus is, probably, in much the same 
condition as those giant orbs — a supposition which is borne out by the spectroscope, as the planet's spectrum 
is similar to those of JuPlTER and Saturn. 

Uranus has four satellites, which revolve round him in rather strangely situated paths (see Plate 14). 
In the case of the moons of Jupiter, and all the other satellites in the system, the paths in which they revolve 
are but slightly inclined to the plane of the ecliptic. The satellites of Uranus, however, move in a plane that 
is inclined at no less an angle than eighty-tivo degrees to the plane in which the planet itself journeys, and at 
this nearly perpendicular position to the planet's orbit, the moons revolve backwards, or from east to west. 

* This is foiind from the " harmonic law," which is, that the squares of the periods of the planets are proportional to the 
cubes of their mean distances from the sun. 



68 



Neptune. 

" Hence the view is profound, 
It floats between the world 
And the depths of the sky." — Goethe. 

This is the most distant member of the sun's planetary family, as at present known. Its discovery was, unlike 
any other in the history of astronomy, made, not by aid of the telescope, but first from mathematical analysis ; 
Neptune being recognised as a planet revolving beyond the distant orbit of UiiANUS, before he had been 
detected with the telescope. Numerous observations had revealed that UilA.NUS was not moving exactly in 
the path, and at the velocity assigned by calculation, even after every known perturbing element had been 
taken into account. This irregularity in its movement suggested to the French geometrician, M. Leverrier, 
and to the English mathematician, Mr. Adams, the existence of a planet revolving round the sun beyond its 
orbit. But these mathematicians went further. They not only suggested that such a planet existed, but 
from Uranus' movements they pointed out the exact part of the heavens where the planet would be seen. 
Direct the telescope to the constellation of Aquarius, wrote Leverrier, to longitude on the ecliptic 326 degrees, 
and a new planet will be found, in appearance like a star of the ninth magnitude. Accordingly the most 
powerful instruments were turned to that part of the sky, and at Berlin, on the evening of the 23rd of Septem- 
ber, 1846, the planet was found, in a place distant from that indicated by calculation less than one degree, or 
scarcely two moon breadths. 

According to calculation it was supposed that Neptune revolved at a distance nearly twice that of 
Uranus, in accordance with the law stated on page 51. Observation, however, soon proved that this was 
not the case, that the so-called Bode's law, though approximately accurate for all the other planets, entirely 
failed in the case of Neptune ; and that, instead of revolving at double the distance of Uranus, the new 
planet made a complete circuit of its orbit in nearly double the period of Uranus' revolution. Neptune, 
therefore, revolves round the sun at an average distance of about thirty times that of our earth, or over 
2,800 millions of miles, and in a period of about 164; years, instead of 3,600 millions, and 217 years 
respectively, as it would have done if obeying Bode's law. 

Neptune is but slightly larger than Uranus, his diameter being about 35,500 miles, so that in volume 

he is ninety times greater than that of our earth. His mass is about eighteen times greater than the mass of 

our globe, which, combined with his great size, shows that like all the other members of the outer planets, he 

is composed of very light materials. In fact, his density is only about one-fifth of the density of terrestrial 

matter, or his globe is about as heavy as if it were formed entirely of water. Owing to the enormous distance 

at which this planet is situated, it is impossible to detect any markings on its surface, or to discover all its 

satellites. One moon, however, doubtless the largest, can be seen with any large telescope. It revolves round 

the planet in 5 days 21 hours, but in a direction opposite to that of the general movements of the 

various members of the system. The planets, we have mentioned, all revolve round the sun in one 

direction, from west to east. The satellites of the planets interior to the orbit of Uranus also move 

round their primary in this direction. The moons of Uranus, however, we have found, are an exception 

to this general rule, as they move in a plane nearly perpendicular to that in which the planet itself 

journeys, in a direction that, though certainly retrograde, may be regarded, from the perpendicular position 

of the orbits, as neither easterly nor westerly. Neptune's satellite travels in a direction that is entirely 

different ; as the inclination of its path to the plane of the planetary orbits is not great, the 

direction of its revolution is distinctly retrograde, or from east to west {see Plate 14). This is also 

thought to be the direction in which the planet rotates on its axis, so that on Neptune the heavenly 

bodies will probably appear to rise in the west and set in the east, 

59 



60 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Trans-Neptunian Planet. 

Neptune is the most distant known planet in the system. Very probably, however, there is another 
planet, if not planets, revolving round the sun beyond his mighty orbit. From the movements of certain 
comets it is thought that the nearest of these far-off planets, if it exists, is situated at a distance, not 
of double that of Neptune's, but at about 4400 millions of miles, and will therefore, as in the case of 
Neptune and Uranus, complete its orbital revolution in double the time occupied by Neptune, or in 
about 330 years. 






S •S' 

■2 "S 









I-2S ' 



t^ 1— I O 

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62 



CHAPTER VI. 

COMETS AND METEORS. 

" Mysterious visitant, whose beauteoias light 
Among the wondering stars so strangely gleams ! 
Like a proud banner in the train of night, 
Th' emblazon 'd flag of Deity it streams — 
Infinity is written on thy beams ; 
And thought in vain would through the pathless sky 
Explore thy secret course." — Conder. 

In ancient times comets virere indeed mysterious visitants, and vi^ere the terror of all beholders. From their 
sudden appearance, their rapid movements, and their gigantic luminous appendages, they were well fitted in 
the unenlightened ages to produce this efifect, and were considered representations of Divine displeasure. 
What is now admired was then dreaded, and looked upon as messengers of death and destruction — as visitors 
from the celestial spaces, whose presence indicated to the superstitious nations, coming famines, wars, or 
plagues. Now we know differently, as science has for ever dispelled these absurd beliefs. It has, by revealing 
their nature, shown that the heavenly bodies, in their silent courses, have not the slightest influence over 
human affairs ; that especially those wandering cometary orbs, however erratic they may appear, certainly 
travel round the sun as much in accordance with the great laws of the universe as do the more regularly 
revolving planets. 

THE PATHS OF COMETS. 

The prophecy of Seneca has thus been fulfilled. About two thousand years ago that philosopher wrote — 
"A day will come when the course of these bodies will be known and submitted to rules, like that of the 
planets." That day has long since come, for about three hundred years ago Tycho Brahd, from his careful 
observations of the comet of 1577, was enabled to demonstrate that comets move at much greater distances 
than that of the moon, and in orbits vastly different from those of the planets, in as much as the comet he 
observed travelled completely through the then supposed planetary crystalline spheres. Kepler, Tycho's 
disciple, considered that the paths of comets were straight, and that their number was as great as the fishes 
in the sea; but it was not till nearly one hundred years afterwards, or about the year 1668, that Hevelius 
first suggested the true nature of cometary orbits — viz., the 'parabolic. From observations of the comet which 
appeared in 1681, tested by Doerfel, this supposition was proved to be correct. The theory of universal 
gravitation having by this time been advanced, a method of computing the different elements of a comet's 
path from three observations was soon invented by Newton, and applied to all comets that appeared.* It was 
in this manner that the true nature of the cometary orbits was finally determined, and several comets identi- 
fied — a triumph of astronomical science that was all the more brilliant from the impossibility of recognising a 

* The so-called elements of a comet's path are :— 1st, the heliocentric longitude of the ascending node of the orbit ; 2nd, the 
inclination of the plane of the cometary path to the plane of the ecliptic ; 3rd, the longitude of the perihelion of the orbit ; 4th, 
the distance of this point from the sun, or the perihelion distance ; and 5th, the exact date when the comet is in this position, 
or the epoch of perihelion passage. 



64 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



comet on its return simply from its appearance. This identification of a comet was first accomplished by the 
astronomer Halley, who discovered that, while some comets moved round the sun in parabolic orbits, others 
undoubtedly formed part of the solar system, and journeyed round the sun in elliptical paths. This he was 
enabled to prove from observations of the comet of 1682. When that orb appeared, Halley, after the method 
invented by Newton, calculated the elements of its path, in order to predict its position in the heavens from 
night to night. In this Halley was so successful that it induced him to try and determine the orbits of all the 
former comets of which accurate observations could be secured. With great labour he computed the elements 
of no less than twenty-four cometary orbits. In examining these he found there were two paths, which were 
almost identical with the comet which had just appeared. Each of these comets had been very conspicuous, 
and what made the coincidence the more remarkable, was the fact that the intervals between the appearances 
of these orbs were nearly equal, for they had appeared in the years 1531 and 1607. Thus between the years 
1531 and 1607, there is an interval of 76 years ; and between 1607 and 1682, there is an interval of 75 years ; 
and further, as these three comets had almost the same orbits, Halley was led to believe that they were 
simply three different appearances of one and the same comet, one probably travelling round the sun in an 
elliptical path in a period of about 76 years. The elements of these comets are as follows : — 



Year in which the comet appeared, ...... 


1531 


1607 


1682 


LoDgitude of ascending node, . 


49° 25' 


50° 21' 


51° 16' 


Inclination of orbit to the ecliptic, ...... 


17° 55' 


17° 3' 


17° 56' 


Longitude of perihelion, ........ 


301° 39' 


302° 16' 


302° 53' 


Distance of perihelion from the sun — the earth's distance as 1 -000, 


0-567 


0-587 


0-583 


Direction of movement, 


Eetrograde. 


Eetrograde. 


Retrograde. 



Halley, however, went further. He not only held that these three comets were different appearances of 
one orb, but that as the comet journeyed in a closed orbit like a planet, it would be again seen 76 years later, 
or in the year 1758. This remarkable prediction was verified; for though the comet did not appear exactly 
at the time given by Halley, but over twenty months later, or in the month of March, 1759, the discrepancy 
was fully accounted for, as its motion had been retarded by the attractions of the larger planets. As might 
be expected, this fulfilment of Halley 's prediction marked an epoch in cometary astronomy; for it proved, 
beyond the possibility of a doubt, that there were some comets bound to our system by the bonds of gravity, 
and revolving in regular periods round the sun. In 1835 this interesting orb again returned. A view of it as 
it then appeared is given in Plate 16, while the position and extent of its orbit will be seen in Plate 13. 



THE MOVEMENTS OF COMETS. 

Comets, therefore, move in parabolic, elliptical, and very often hyperbolic orbits. In fact, it is highly 
probable that though comets are sometimes considered to travel in the first-mentioned curve, they never really 
do so, but on the contrary move either in a long elliptical, or hyperbolic path. In every instance the sun is 
situated in the focus of the curve, and in this respect the paths of comets are identical with the orbits of the 
planets. Unlike the planetary paths, however, the orbits of comets are not confined to a general plane, but 
are inclined to the plane in which the planets move at all angles ; some comets, indeed, move in planes nearly 
perpendicular to those of the planets. The direction of the movement of comets is also in some cases different 
from the movements of the planets. The various members of the planetaiy system revolve round the sun all 
in one direction, — viz., from west to east {see Plate 13). This is also the direction in which the sun, and planets, 
out to the orbit of Ueanus, rotate on their axis, and also that in which the various satellites of these planets 
revolve in their orbits. Many comets also move round the sun in this direction, but as great a number are found 
to travel in a direction exactly opposite, or from east to west, as in the case of Halley 's comet (see Plate 13). 



THE MORE IMPORTANT COMETS BELONGING TO THE SOLAR SYSTEM. 

First Class, with short periods. 



NAME OF COMET. 


Mean Distance from the 
Sun (Earth's as 1000). 


Period of Revolution. 


Eccentricity of OthU. 


Inclination of Orbit to 
Plane of Ecliptic. 


Direction of iiotion. 


Encke'6 .... 


2-22 


3 -3 1 years. 


0-846 


12" 54' 


Direct. 


Blainpain's 




2-84 


4-81 „ 


0-687 


9" 11' 


)) 


Burckhardt's . 




2-93 


5-03 „ 


0-864 


8' 2' 


)) 


Clauseus' . 




309 


544 „ 


0-721 


r 54' 


" ; 


Brosen's . 




3-10 


5-46 „ 


0-810 


29" 23' 


:) 


Tempel-Swift's 




3-12 


5-51 „ 


0-656 


5" 24' 


>> 


Lexell's . 




3-16 


5-61 „ 


0-786 


1° 34' 


1 


Pons's 




3-16 


5 62 „ 


0-755 


10" 43' 


>) 


Winnecke's 




3-23 


5-81 „ 


0-727 


14" 27' 


)i 


Tempel's . 




3-49 


6-51 „ 


0-405 


10" 50' 


»» 


Biela's . 




3-53 


6-63 „ 


0-755 


12° 34' 


» 


D'Arrest's 




3-55 


6-69 „ 


0-626 


15" 42' 


11 


Faye's 




3-85 


7-57 „ 


0-549 


ir 20' 


11 


Pigott's . 




4-65 


10-03 „ 


0-679 


47" 43' 


11 


Suttle's . 




5-74 


13-76 „ 


0-822 


55" 14' 


11 


Peters's . 




6-32 


15-99 „ 


0-757 


13° 2' 


" 


The above Comets are all invisible to the naked eye, being 


what are known as Telescopic Comets. 




Second Class, with mean periods. 




Westphal's 


16-62 


67-77 years. 


0-925 


40° 58' 


Direct. 


Pons-Brook's . 


17-22 


71-48 „ 


0-955 


74° 3' 


11 


Olber's . 


17-41 


72-63 „ 


0-931 


44° 34' 


J) 


De Vice's 


17-54 


73-25 „ 


0-954 


84" 57' 


j> 


Brorsen's .... 


17-78 


74-97 „ 


0-973 


19" 8' 


11 


Halley's .... 


17-99 


76-37 „ 


0-967 


17" 45' 


Retrograde. 


Third Class, with l 


ONG PERIODS 






Year in which Comet appeared. 


Perihelion Distance 

(Earth's mean distance 

as 1-000). 


Period of Recolution. 


Eccentricity of Orbit. 


Inclination of Orbit lo 
Plane of Ecliptic. 


Direction of Motion. 


1580 A.D. 


0-602 


9,000 years. 


0-998 


64" 34' 


Direct. 


1680 


0-006 


8,800 „ 


0-999 


60" 40' 


» 


1811 


1-035 


3,000 „ 


0-995 


73° 2' 


Eetrograde. 


1822 


1-145 


5,500 „ 


996 


52° 39' 


» 


1830 


0-921 


6,000 „ 


0-999 


21° 16' 


Direct. 


1840 


1-481 


14,000 „ 


0-998 


59° 13' 


Retrograde. 


1844 


0-855 


102,000 „ 


0-999 


48° 36' 


u 


1858 (Donati's) 


0-578 


2,000 „ 


0-996 


63° 2' 


)) 


1863 


0-795 


1,800,000 „ 


0-999 


85° 22' 


Direct. 


1864 

i_ 


0-931 


2,800,000 „ 


0-999 


70° IS' 


Retrograde. 



65 



66 ~ A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



Periodic comets, or those revolving in elliptical paths, may be divided into three separate groups — viz., 
comets with short periods; those with mean periods; and those with long periods. The more important 
members of the various classes are given in the Table on p. 65. 

The one with the shortest period of revolution — Encke's — was discovered to be periodical in the year 1818, 
though it had frequently been observed on former occasions, as far back as the year 1789. As this small 
comet came to be watched it was discovered that its period of revolution was gradually decreasing in length. 
This could only be accounted for by supposing that there existed in what had hitherto been called empty 
space, a very rare medium, which, however, was dense enough to sensibly retard the movements of the smaller 
comets. This resisting medium is now known to exist. In Chapter V. it was mentioned that the sun is 
surrounded with an exceedingly complex atmosphere, which is so extensive as probably to reach to the confines 
of the system. The more distant, of course, a portion of this atmosphere is from the sun, the rarer it becomes, 
and beyond the orbit of our globe it is doubtless so attenuated as to be incapable of producing much retarda- 
tion on the motions of even the lightest comets. Near the sun, however, it is different ; the density of the 
solar envelope is greater, and therefore when a small comet, as in the case of Encke's, happens to pass so near 
the sun as to be within the orbit of Mekcurt, the resistance encountered is sufficient to give the central orb 
power to draw the comet into a smaller path, and accordingly accelerate its movement, and shorten its period of 
revolution. All the comets of the first two classes, with the exception of Halley's (see Table), move round the 
sun in the same direction as the planets, or from west to east, and their movement is therefore said to be "direct." 
Those which travel in the opposite direction, or from east to west, have accordingly a retrograde movement. 

The comets of the third class have periods extending from 200 years and upwards. In most cases the 
intervals of revolving round the sun are not known with certainty, as that part of the elliptical path traversed 
by the comet during the time it is visible, differs very little from a true parabola. It is, therefore, with the 
utmost difficulty that even the approximate mean distance can be determined, and as the periods are so long, 
two visitations from a member of this class have not, so far as is known, been observed. In fact, the interval 
occupied by some periodic comets in revolving round the sim is so enormous, that when last visible firom our 
globe no astronomers were probably here to observe them. Indeed some comets may have periods amounting 
to over three millions of years, and may travel so far into space as to be over one thousand times more distant 
from the sun than Neptune, or to a distance from the central orb of about one-fifth of the distance which 
separates us from the nearest star— a distance that even light would require about ten months to journey over. 
Indeed, there is no limit to the distance to which some comets may travel ; only if they recede from the sun 
beyond a certain distance, or move away from him above a certain velocity, they will be brought within the 
sphere of some other sun's influence, and journeying towards the new centre of attraction, will never again 
visit our system. 

THE HEADS OF COMETS. 

In general the head of a comet, when viewed with the telescope, appears as a bright condensed and sometimes 
star-like nucleus, surrounded with several vaporous envelopes. This bright portion is really the principal part 
of the comet, for it alone strictly obeys the solar attraction, and moves in a true elliptical or hyperbolic orbit 
In most large comets the nucleus consists of a solid, liquid, or vaporous mass, depending on its distance from 
the sun. When very near the sun, it of course glows with intense heat — so intense, indeed, that the most 
refragable material known will easily be vaporised. The head of the comet of Newton which appeared in 
1 680, for instance, approached the surface of the sun as close as one-third of the solar diameter, and was 
accordingly subjected to a heat nearly 26,000 times greater than that of the sun in our tropical regions, 
or over 2000 times greater than the temperature of red-hot iron. Under the action of the solar heat 
the nucleus appears to decrease, a result which would not be expected, as the effect of an increase of tempera- 
ture is rather to expand the mass. This will certainly be the case with the heads of all comets on their 
approacli to the sun; but as the real nucleus will also become brighter, and the vaporous masses surrounding 



Comets— Plate 




COMETS AND METEORS. 



67 



it be made more transparent, the apparent size of the head will be less. The appearance of the brightest part 
of the head alters also with increase of telescopic power ; for the larger the instrument employed, the smaller 
it appears ; this indicates that even in a large comet the real nucleus is very small indeed, and is greatly 
obscured by the vapours surroimding it. 

The luminous material in which the nucleus is enclosed, is, from its hairy appearance, called " the coma." 
In many instances the spectroscope shows that the vapour of which it is composed consists largely of hydrogen 
and carbon in one of their more numerous compounds. In large comets streams of matter are often observed 
moving in the coma, travelling outwards from the nucleus, like waves receding from the place where a stone 
has been dropped into some still water. These envelopes, as they have been termed, are doubtless spherical 
segments of matter, slightly more dense than the vapour forming the other parts of the coma — {see the heads 
of the comets of 1861 and 1882 in Plate 16). Even these densest portions, however, consist of some very 
rare vapour, as is proved by the fact that faint stars can occasionally be seen shining through them. In the 
direction exactly opposite from the sun the coma generally streams past the nucleus, and forms the commence- 
ment of the tail. 

THE TAILS OF COMETS. 

The tail is certainly the most wonderful portion of a comet — the part which, from its strange appearance 
and gigantic dimensions occasionally attained, was, in superstitious ages, well fitted to produce terror and awe. 
In telescopic comets the tail, as might be expected, is generally small, and sometimes altogether wanting, in 
which case the comet is simply a mass of vapour without any distinct nucleus. In travelling towards the sun, 
the tail is always stretching behind the nucleus, and before it when the comet is travelling away from the 
centre of attraction. This was first noticed to be the case by Appian, from observations of the comet which 

THE APPARENT AND ACTUAL LENGTHS OF THE TAILS OF COMETS. 



Name of Comet. 


Apparent Length of 
Tail in Degrees. 


Actual Length in 
Millions of Miles. 


Name of Comet. 


Apparent Length of 
Tail in Degrees. 


Actual Length in 
Millions of Miles. 


1860 (in.) 


15° 


22 


837 


79° 




1744 


24° 


19 


1680 


90° 


150 


1811 (i.) 


25° 


109 


1769 


97° 


40 


1811 (II.) 


... 


130 


1264 


100° 


... 


1456 


57° 


... 


1618 (II.) 


104° 


50 


1843 (I.) 


65° 


200 


1647 (i.) 


... 


131 


1858 


64° 


55 


1861 (II.) 


118° 


42 


1689 


68° 


... 









appeared in 1531, as he found that independent of the position the comet occupied in its orbit, the tail was 
always pointing away from the sun, and was simply a prolongation of the radius vector, in every instance the 
convex side being nearest to that line. 

In many instances the tails of comets extend to an enormous distance from the nucleus. The tail of the 
comet of Newton, for example, was no less than 100 millions of miles in length, and consequently extended 
from the sun to a distance greater than that which separates our earth from the centre of the system. But 
the great comet which appeared in 1843 had even a larger tail — one, in fact, of nearly double the length. 
The lengths of the tails of the largest comets are given in the above Table. 

But while the tails of comets occasionally extend to enormous distances, they are always formed of the very 



68 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



rarest materials. This is proved to be the case from the fact that often the faintest stars are seen shining 
through even the densest portion, without their light being greatly diminished, notwithstanding the enormous 
depth of vapour which the light has to pass through. This shows that the total amount of matter in the tails 
of even the largest comets must be very insignificant. In many cases, indeed, it may only weigh a few ounces, 
though the tail be hundreds of millions of miles in length. It is, in fact, from its extreme lightness that the 
tail stretches to so great a distance ; for the matter composmg it is being continually formed of new 
material. Under the action of the solar heat, the matter in the nucleus is partly converted into vapour, and 
the more volatile the substance the greater the distance to which it is expelled. This expulsion of the 
vapour from the nucleus is brought about by a force directed from the sun, acting on the rarer materials 
and driving them to great distances. This is the cause of the tail pointing away from the sun, and why 
it often appears curved and of double or multiple form. The different materials of the nucleus will, in 
proportion to their mass, be, of course, expelled with different velocities, and tails of various forms will be 
produced. As hitherto observed, the tails of comets can be arranged into three forms. First, long, straight 
tails; second, long, curved tails; and, third, short, broad, curved tails, deviating greatly from the radius vector. 
The first class is well represented by the comet of 1843 {see Plate 16). This type of tail is evidently 
composed of some very light vapour, probably the lightest known gas, or hydrogen, which, from its rarity, will, 
under the repulsive force, attain the greatest possible velocity— a velocity great enough to prevent the tail 
from becoming curved. The matter of the second type is possibly heavier, being doubtless hydro-carbon gas. 
Accordingly, as m the case of Donati's comet (see Plate), the tail assumes a graceful curve. In the 
third type, the matter is still heavier, for the velocity of the particles is least, as revealed by the shortness 
of tail, and the amount of deviation or dragging behmd the nucleus. Doubtless this type of tail is composed 
of the vapour of iron. 

METEORS. 

The tails being always composed of fresh material, comets are accordingly becoming gradually smaller. 
At each perihelion passage large quantities of the more volatile substance in the nucleus are dissipated, and, 
consequently, the tail becomes shorter at each successive return. Halley's comet is a striking example of this. 

In the past its tail was large, and it appeared as a conspicuous object ; 
but on the last return, in 1835, the tail was comparatively insignifi- 
cant. In the case of Biela's comet, on the other hand, the combined 
action of the solar rays, and the repulsive force, finally produced a 
disintegration of the vaporous mass. This is doubtless the end of 
all comets ; their materials being distributed along their orbits in the 
form of revolving streams of small particles of matter. These streams 
are very thickly strewn throughout the solar system, and must thus 
be frequently encountered by the planets. Indeed, our own planet 
comes into contact very often with these meteoric clouds, and in so 
doing brings about a shower of shooting stars. From the attraction 
of our earth, the particles of matter iu the stream are drawn with 
great velocity to her surface. As they near our globe their speed is so very great that whenever they 
enter the atmosphere the resistance they meet with generates an intense heat, which is generally more than 
sufficient not only to ignite the meteoric matter, but to completely dissipate it before reaching the ground. 

As the cometary or meteoric streams cut the orbit of the earth at various places, our globe will therefore 
pass through each one that does so, once in every revolution, or annually. Accordingly, the display from a 
given system will occur regularly on certain dates, and will also appear to come from the same part of the 
heavens. Those meteors, for instance, which are seen on the 12th and 13th of November appear to radiate 
from a part of the heavens near the star j Leonis (see Fig. 17) ; those of the 27th of the same month from 




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69 



70 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



the constellation of Andromeda ; and those seen on the 10th of August, from the constellation of Perseus. 
The Table on page 69 contains the more important "radiant points" of meteor systems, or that part of 
the heavens from which the meteors appear to burst. 

OCCURRENCE OF METEOR SHOWERS. 

As might be expected, the display from a meteor system is not annually the same, owing to the likelihood 
of the matter composing the stream being unequally distributed in its orbit. This is, indeed, found to be the 
case with the principal meteor systems. The meteors of the 13th November, for example, have a maximum 
display once every thirty-three years, and the last great shower from this system took place in 1866. The 
meteors of the 27th November, again, had their last maximum display in 1885, on which occasion the heavens 
were alive with brilliant celestial fireworks. This system is identified with the periodic comet of Biela, a 
comet that has been lost since 1852. Discovered in 1826, this comet had been seen on its various returns to 
perihelion till 1846, when it was noticed that it became divided into two parts. In 1852 the double comet 
was again seen, but since then it has never been observed, the vaporous masses having doubtless been further 
dispersed and scattered along their orbits. On the 27th of November, 1885, however, part of this comet 
was seen indirectly, by our earth coming into contact with it, and producing the magnificent meteoric shower. 

On the above-mentioned occasion the number of meteors caught by our globe must have been enormous. 
This shows us that the annual quantity of material received by our planet is very great indeed. In the past 
it was doubtless even greater, as by repeated encounters, not only with the earth, but many of the other 
planets, the various meteor streams have been greatly destroyed. In fact, at one time the amount of this 
meteoric material in the solar system would probably be so great as to have sensibly increased the diameter 
and mass, not only of our own globe, but of each of the planets. For the most part the individual shooting 
stars are of small dimensions, and probably weigh but a very few ounces. Though coming from the regions 
of interplanetary space they do not, as might have been supposed, bring any new element, but are composed 
of many well-known terrestrial substances, as iron, nickel, &c. This is found to be the case from analysis 
of the meteoric dust brought down from the higher atmosphere by snow, and found on the top of high 
mountains where the soil has not been disturbed. 



METEORITES. 
Sometimes individual meteorites are of a much greater size and weight than those above mentioned, being 
in many instances actually large enough to prevent the resistance of the atmosphere from completely destroying 
them, and accordingly the mass reaches the ground in a solid state. These meteoric masses which thus 
occasionally fall have all the appearance of ordinary stones, and are generally of a greyish colour. They have 
been arranged into three classes, according to the nature of their composition. First, Aerolites, which are 

simply masses of stone composed of different silicates, 
interspersed with particles of nickeliferous iron, and 
protosulphide of iron; second, Siderites, or masses of 
iron containing phosphides of nickel, and sometimes 
carbon ; and, third, Siderolites, or large sponge-like 
masses of nickeliferous iron, with various silicates in 
the cavities. The siderites are by far the heaviest of 
the meteorites, one at the Kensington Museum actu- 
ally weighing three and a-half tons. It is fortunate 
for science that these masses occasionally fall, as they 
can be analysed, and accordingly not a little learned, not only of their present structure, but what is of greater 
importance — vi^., of their condition in the past. When analysed their composition is found to be, for the most 




Fig. 18. metkoric stones. 



COMETS AND METEORS. 



11 



part, of the same nature as meteoric dust, and therefore no new element has been found, which shows that even 
in the distant celestial regions the same kind of matter exists as on our earth — a testimony which is also borne 
out by spectroscopic analysis of the stars. The following are the different elements which have been found in 
meteorites : — 



Hydrogen. 

Oxygen. 

Chlorine. 

Sodium. 

Potassium. 

Carbon. 



NickeL 

Iron. 

Cobalt. 

Copper. 

Tin. 

Calcium. 



Magnesium. 
Aluminum- 
Arsenic. 
Antimony. 
Titanium. 
Lithium. 



Manganese. 
Chromium- 
Sulphur. 
Phosphorus. 
Vanadium. 
Silicon. 



ORIGIN OF COMETS AND METEORS. 

Besides revealing the nature of their composition, analysis also shows that at one time these solid 
meteoric masses existed in a state of hot vapour, which on cooling condensed into many minute particles, which 
afterwards collected into larger masses and solidified. This result is what might be expected from the con- 
nection which exists between meteors and comets. Analysis throws some light also on the origin of 
comets themselves. When, for instance, certain of the iron meteors are heated in a vacuum, they give off a 
very large quantity of hydrogen, which shows that they must have been ejected from some dense atmosphere 
of that gas. In Chapter III. it was mentioned that the stars of the first type had exceediugly dense atmo- 
spheres composed of hydrogen, and so one is led to suppose that it was from some of those distant orbs that 
these particular meteorites have come. At first this would seem to be impossible, but it is not by any means 
so. Our sun, as mentioned in Chapter V., has power to occasionally eject matter from his surface to very great 
distances, and what is true of our sun is also true of every star in the heavens, especially the stars of the first 
class. From some distant sun, then, a quantity of the glowing vapour surrounding it would, from the effect 
of a gigantic eruption, be ejected with a velocity greater than that which the star itself could impart to objects 
falling towards its surface. In consequence of this, the vaporous mass would for ever travel away from the 
sun from which it was expelled, and, in so doing, would condense, perhaps into one large mass and form a 
comet, or into numerous minute particles, and produce a swarm of meteors ; or it may be, produce both of 
these results. 

The origin of the larger comets and meteor streams travelling from the regions of inter-stellar space is 
thus accounted for, but it does not explain the existence of the very small periodic comets. A striking 
peculiarity of these small orbs is that the aphelia of their orbits are always situated near the path of some 
large planet. In every case, when farthest from the sun, the comet is close to the planet's orbit, a fact which 
points to some connection between these small comets and the giant members of the outer planets. Indeed, it 
is thought that most of the small periodic comets are simply the outcome of eruptions on the giant planets, at 
a time in the distant past, when those orbs were in a condition greatly different from that in which they are 
at present — when they were in a more youthful stage, and were glowing with intense heat, and giving out 
light like miniature suns. 



CHAPTER VII. 

THE MOON. 

" All hail ! thou lovely queen of night, 
Bright empress of the starry sky ! 
The meekness of thy silv'ry light 

Beams gladness on the gazer's eye." — Miller. 

THE LUNAR PHASES. 

On certain evenings during every month, shortly after sunset, the moon may be seen shining in the western 
part of the sky, as a very slender crescent of light. This crescent will be observed to increase in dimensions 
from night to night, till in about seven days after it was first noticed, it will appear as a half-illuminated 
disc. As is well known this is called half-moon, or the moon's first quarter. The lighted portion of the moon 
steadily increases, and in about other seven days it is seen perfectly round, or the moon appears full. From 
this time the bright part of the lunar disc gradually decreases, till in about a week after full moon, at 
the time of the last quarter, the moon once more appears as a half-luminous disc ; and in about fifteen 
days after the full, she is invisible, being then nearly between our earth and the sun. This portion of 
the lunar globe, when in conjunction with the sun, is termed new moon; and from careful observations it 
has been found that the mean interval between each of these phenomena is 29 days 12 hours 44 minutes 
27 seconds. 

These different appearances of the moon are known as phases, and are produced by the revolution of the 
moon round the earth, which has the effect of bringing into view various portions of the illuminated half of her 
globe. At the time of new moon, for instance, when the lunar globe is between us and the sun, all the lighted 
side is directed away from us ; but as the moon in revolving round our earth travels to the eastward of 
the solar orb, more and more of the western part of the illuminated side is brought into view, till, when 
directly opposite to the sun, the whole of the lighted half is turned towards us, and the moon then appears 
full. From the point of opposition to the solar globe, the moon in completing her orbital revolution now 
gradually approaches the sun, and accordingly the western side of the illuminated disc begins to diminish. In 
about a week afterwards, by the time the moon has journeyed to within ninety degrees from the sun as viewed 
from our earth, the disc again appears half-illuminated, as when in the opposite part of her monthly path at 
the time of the first quarter, with this difference, now the bright half is turned in the contrary direction, or to 
the east. 

As above mentioned the intervals between successive conjunctions of the sun and moon, or the com- 
plete period of a lunation, is a little over twenty-nine and a-half days. This period, however, is longer than 
the time occupied by the moon in making a complete revolution round our globe. The length of the lunar 
orbital revolution can be accurately determined by observing the time occupied by the moon in travelling from 
a star, right round the heavens, back to the same star again. This is termed the sidereal revolution of the 

moon, the time required for which amounts to 27 days 7 hours 43 minutes 11-5 seconds, or over two days 
72 



THE MOON. 73 



shorter than a lunation or synodical revolution. The difference between these periods is produced by the 
moving of our globe round the sun, for if the earth had no orbital movement the two periods would be of 
exactly the same length. Our globe, however, like each of the planets, is constantly travelling round the great 
centre of the system, moving at the angular velocity of about one degree per day ; which has the effect of 
causing the sun apparently to move round the heavens among the stars in an easterly direction, at the same 
angular velocity. The moon, on the other hand, from her own orbital movement, journeys round the heavens 
in the same direction as the sun, but at the apparent velocity of over thirteen degrees per day. By the time, 
therefore, the moon has travelled from conjunction with the solar orb completely round the heavens, or made a 
sidereal revolution, the sun has apparently journeyed twenty-seven degrees to the eastward of the position he 
occupied when the lunar globe was last in conjunction with him. Accordingly, the moon moving at the rate 
of thirteen degrees per day will occupy two days longer than a complete revolution, or in all twenty-nine and 
a-half days, in order to be again in a line with the sun. 

THE MONTH. 

From what has been mentioned, it will be seen that there are different kinds of months, depending on the 
manner in which they are determined. The oldest one was undoubtedly the synodic, as it was easily deter- 
mined from the phases, it being, as already mentioned, the interval between successive conjunctions of the sun 
and moon. This, indeed, was the earliest year, or longest time-interval of primitive man, and from the 
change occurring once in about every seven days, the worshipping of the moon at these intervals ultimately 
gave rise to the invention of the week. The sidereal month, or interval between successive conjunctions of the 
moon and a star, as already mentioned, is shorter than the synodic, but it is the true length of the moon's 
orbital revolution, and this period being determined from the stars, is consequently subject to no variation. 
The tropical and nodical months, or intervals between conjunctions of the moon and a trojiic, and the moon 
and the node, respectively, are still shorter, on account of the movements of these points being in the opposite 
direction to that of the moon in her orbit. 

Owing to the precession of the equinoxes, the tropical and solstitial points are carried round the heavens 
from east to west ; and, accordingly, the period of revolution when determined from either of these points will be 
slightly shorter than the sidereal period. The nodical month is also shorter for a similar reason, as the nodes 
of the lunar orbit revolve round the ecliptic from east to west, or retrograde, in a period of over eighteen and 
a-half years. Accordingly, while the moon has journeyed from a node completely round the heavens, the node 
has, meanwhile, travelled about one and a- quarter degrees to the west of its former position, and the moon will 
come once more in conjunction with it, nearly three hours before a sidereal revolution has been completed. 
The anovialistiG month, or the interval occupied by the moon in travelling from some jjoint in her orbit back 
to the same point again, on the other hand, is slightly longer than the sidereal month, as the line of apsides of 
the orbit, or the line passing through the perigee and apogee, revolves round the earth in the same direction 
as the moon, or from west to east. If, therefore, the perigee be the point from which the period is determined, 
it will be longer than a sidereal revolution by five and a-half hours ; because during the time the moon has 
made a circuit of her orbit, the perigee has advanced about three degrees. The following are the lengths of 
the different months : — 

Mean synodical month (from new moon to new moon), 
Anomalistic month (from perigee to perigee), 
Sidereal month (from star to star), . . . ■ 

Tropical month (from equinox to equinox), , . . 

Nodical mouth (from node to node), .... 

73 



)ays. 


hrs. 


mm. 


sec 


29 


12 


44 


2-68 


27 


13 


18 


37-44 


27 


7 


43 


11-55 


27 


9 


43 


4-68 


27 


5 


5 


3581 



u 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



THIC LUNAE ORBIT. 

The moon is the nearest of all the heavenly bodies, being situated from us on the average at a distance of 
about 240,000 miles. As in the case of the planets, the path in which the moon journeys round the earth 
deviates considerably from a circle. The eccentricity of her orbit amounts, in fact, to about 0'055, or one- 
twentieth of the semi-major axis. Owing, however, to the perturbing influence of the sun, this quantity is 
subject to a variation of about O'Ol on either side of the mean value above-mentioned ; or the eccentricity 
alters between the limits of 0'04<4 and 0"066. The distance of the moon from the earth, therefore, alters to 
the extent of about 31,000 miles ; the maximum distance being 252,948 miles, and the minimum 
distance 223,593 miles. As already mentioned, the perigee and apogee, or those points in the orbit which are 
nearest to, and farthest from, the earth, do not always occupy the same position, but move round the ecliptic 
in an easterly direction. Sometimes, however, they slowly retrograde, but never for a very long period, and 
therefore the direct movement predominates, advancing at the annual rate of about forty-one degrees, and 
making a complete revolution of the ecliptic in nearly nine years. 

The path in which the moon travels is not situated in the same plane as that of the terrestrial orbit, but 
is inclined to it at an angle of about five degrees. Like the eccentricity, the inclination is also subject to 
variation from the altering position of the sun with respect to the earth and moon. Its greatest value amounts 



,e^TS^"■^ 



ORBirOFTHE-fARTiT^ 
IV QUARTER 



r&«^-__ 



**-Ct-^L 




Fig. 19. {A} True Path of Moon ruund the Sun. {B) False Path as Formerly Eepresented. 



to 5 degrees 13 minutes ; its least value 5 degrees 3 minutes. Those diametrically opposite parts of the lunar 
orbit, called the nodes, which cut the ecliptic plane, are not stationary, but move along the ecliptic at the rate 
of 19 degrees 21 minutes per year. Accordingly, they make a complete circuit of the heavens once every 18"6 
years, and in doing so journey in a retrograde direction, or from east to west. 

But the moon moves in another orbit besides the one she describes every month, for while she is revolving 
round our globe she is also, like our earth, obeying the solar attraction, and, therefore, moves round the sun 
in a path which differs but little from that traversed by our planet. The annual lunar orbit is slightly 
elliptical, and strange as it may at first seem, it is always concave to the sun. If, for instance, we could 
watch the movement of the moon from a point in space near the sun, we would notice that our satellite 
travelled round the centre of the system like any other planet. Sometimes, of course, it would be observed 
that she was between us and the earth, and occasionally farther away than our globe ; but these differences in 
her distance are so exceedingly small in comparison with the distance of the earth that they could only be 
detected with diflSculty. Fig. 19 is an accurate representation of a small portion of the annual lunar orbit, 
from which it will be seen that all the effect produced by the monthly movement is, at the time of new moon, 
to slightly flatten its solar orbit, and at the time of full moon to make it slightly more curved. The moon, 
therefore, though a satellite of our earth, is also a planet revolving round the sun, and as her average distance 
from the centre of the system is the same as that of our own globe, her year is equal to ours in length. 



THE MOON. 



75 



DIMENSIONS OF THE LUNAR GLOBE. 

Besides being the nearest heavenly body, the moon is the smallest orb that can be seen without telescopic 
aid. But while this is the case, our satellite is not by any means an insignificant globe. Her diameter is 
about one-fourth of that of the earth ; or, more exactly, 2163 miles (see Fig. 20). The surface of the lunar 
globe, accordingly, contains nearly 15 millions of square miles, and is less than one-thirteenth of the 
surface of the earth, or about the same as the combined area of North and South America. Between 
the volumes of the earth and moon there is even a greater difference. The volume of the moon is only 
one-fiftieth of that of the earth, or it would require fifty globes the same size as the moon to form a 
globe equal to ours in size. The greatest of all differences, however, is found between the masses of 
the two globes, as the lunar material is not nearly so heavy as the matter forming our earth. The 
average density of terrestrial material is 5".58 times that of water ; the lunar material, on the other 
hand, is only 3"4 times the density of water. 
Accordingly a cubit foot of terrestrial matter is 
heavier than an equal portion of lunar material 
in the proportion of three and a-half to five and 
a-half; and, consequently, while it requires fifty 
globes the same size as the moon to form a 
sphere equal to that of our earth, it requires no 
less than eighty moons to make a globe equal 
to the earth in mass. From this it follows that 
the attraction of gravity on the lunar surface, or 
the force with which bodies are drawn downwarc?s 
will be considerably less than it is here. If the 
moon were the same size as our globe this force 
would be exactly one-eightieth of the surface gravity 

on earth ; but as her diameter is over one-fourth of the terrestrial diameter, and as the force increases with 
the square of the decreasing distance from the centre of the sphere, it is therefore on the lunar surface about 
one-sixth of the attraction on the surface of our globe. 



^^ 


• 


■■Bh 


THE EARTH , 


THE MOON 



Fig. 20. the comparative sizes of the earth axd iioon. 



THE ROTATION OF THE MOON. 

Like our earth and each of the planets, the moon rotates on her axis, but in a somewhat different manner. 
In the case of the planets, the rotation periods are not of any great length, and differ greatly from the period 
of revolution. The lunar rotation, on the other hand, is comparatively long, and curiously enough coincides 
exactly with the monthly orbital revolution, This is the most remarkable circumstance known about the 
moon. This fact was discovered shortly after the telescope was invented, as that instrument soon showed 
that the same side of the lunar globe was always directed to the earth. Accordingly but little more than 
one-half of her entire surface has ever been seen, as the moon presents exactly the same appearance to us as 
she did to Galileo when first he saw it with his telescope. 

The cause of this coincidence of the rotation and revolution periods of the moon is entirely owing 
to the shape of the lunar globe. In past ages, when the moon was in a molten state, she must have rotated 
much more rapidly than at present. As her globe cooled, however, the rotation would become gradually 
slower, owing to the retardative influence of the attraction of the earth. This would, in fact, be 
sufficient to produce an effect similar to that brought about by the moon on our oceans ; for the attraction of 
our globe would actually raise part of the lunar surface, or create a tide in the soft, and, as yet, hot matter of 
the lunar globe. This would retard the rotation, and to such an extent, that ultimately it would coincide 
with the time occupied by the moon in making a complete revolution of her monthly orbit. At the same 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



time, the diameter of the lunar globe, now always directed to the earth, would become slightly more elongated, 
and, therefore, the moon, instead of being truly spherical, is slightly bulged earthwards. 

As might be expected, the movement of the moon on her axis is perfectly uniform. The velocity in her 
orbit, however, is far from being so, and, consequently, slightly more than a complete half of the lunar globe 
is seen during an entire circuit. If the moon moved in a circular orbit, her angular movement would be 
regular, and only the one half of her surface would be visible. But, instead of this, the path of the moon 
round the earth is very elliptical, and accordingly the lunar movement is faster at perigee and slower at apogee 
than the mean value. Between these opposite parts of the orbit, the moon's position in her path differs by 
as much as six degrees from the place she ought to occupy if she had been moving in a circular path, or at her 
mean angular velocity. At these positions, then, the greatest amount of the invisible hemisphere of the moon 
will be brought into view, v;hile, on the other hand, near the perigee and apogee, the lunar disc will assume its 
normal appearance. This apparently alternate swaying of the lunar globe on either side of its mean position 
is called the libration in longitude. But not only are the east and west sides of the lunar disc alternately 
brought into view, the north and south portions also become visible. This is known as libration in 
latitude, as it depends on the varying position of the moon from the plane of the earth's orbit, or the 
lunar latitude. The axis of the moon not being perpendicular to the path in which she moves, the north 
and south poles of her globe are in succession directed towards the earth, and brought into view during a 
complete revolution. 

As the nodes of the lunar equator coincide with those of the orbit, both of the lunar poles are visible at 
the time the moon is near the nodes of her orbit ; while, at the time of the greatest distance from the nodes, 
the maximum amount of inclination of her axis towards the earth takes place. When at her farthest from 
the plane of the ecliptic, or at her greatest latitude north, the lunar equator is tilted slightly upwards, and the 
south pole of the moon is accordingly brought into view. At the greatest southern latitude, the opposite effect 
takes place, the north pole is visible, and the equator tilted towards us. The amount of apparent swaying 
thus produced is nearly the same as that of the libration in longitude, or more exactly 6 degrees 44 minutes. 

There is still a third libration, one, however, not produced by the moon itself, but by the varying position 
of the observer on the surface of our globe. When, for instance, the moon is rising, more of the western edge, 
and, when setting, more of the eastern side is seen than when the moon is on the meridian. This is called 
diurnal libration, which, as mentioned, is the effect of lunar parallax, and, consequently, amounts to slightly 
over one degree. This phenomenon, as well as the libration in latitude, was discovered by Hevelius, who also first 
explained the libration in longitude. From the combination of these three librations, considerably more 
than one-half of the lunar surface is rendered visible. About four-tenths of the surface is always visible, and 
nearly the same amount is at all times unseen, while nearly two-tenths is alternately visible and invisible. 

TELESCOPIC APPEARANCE. 

When the lunar disc is viewed with the telescope, it appears to be covered with numerous dark patches. 
Several of these are so large as to be easily seen with the unaided eye, and when thus viewed near the 
time of full-moon, they form a likeness to a human face, from which resemblance there doubtless originated 
the idea of " the man in the moon." Before the telescope was invented, these dark markings, seen on the 
illuminated lunar disc, were supposed to be seas, as the moon was believed to be a world very much like ours. 
The telescope, however, soon revealed that this was not the case ; for, instead of being a globe like our earth, 
with large tracts of water on its surface, not the .slightest vestige of water or air was visible. The dark parts 
were, therefore, found to be large level portions of the lunar surface, or extensive plains, and not lunar 
seas, as had been supposed. 

In the chart of the moon at the end of the volume, and also in the photographs at the frontispiece, the 
size and position which these plains occupy on the lunar surface will be clearly seen. Though the moon is 



THE MOON. *!'j 



not nearly so large a globe as our earth, these level portions are of considerable dimensions. The Sea of 
Serenity, for instance, which is nearly circular in shape, has an average diameter of 430 miles, and, therefore, 
has an area equal to that of France ; while the Sea of Crisis, though smaller than the Sea of Serenity, has au 
area about equal to that of England and Wales, or covers the one-ninety-fouith part of the visible lunar 
surface. The general level of the surfaces of these so-called seas is more depressed than the average level 
of the whole surface of the lunar globe. In fact, the Sea of Crisis is so much depressed that the mountains 
on its eastern side rise from its surface to a height of about three miles. In long past ages, when water 
undoubtedly existed on the moon, these lower portions would be completely filled, and are thus nothing more 
than the bottoms of dried-up lunar oceans. This being the case, it is not difficult to understand how the 
colour of these plains is somewhat different from other parts of the lunar surface, for vast quantities of dark 
muddy matter was doubtless carried down by the lunar rivers, and deposited in the once active oceans. 

LUNAR MOUNTAINS. 

Though not nearly so numerous as on our earth, there are on the moon several ranges of mountains. 
These, like the terrestrial ranges, run for the most part along the sides of what were at one time the principal 
oceans. By far the most conspicuous of these ranges is known as the Apennines, a chain which extends to a 
distance of 460 miles along the south-west border of the Sea of Showers. The mountain peaks on this range 
are very numerous, and rise to great heights. In several instances they attain altitudes of no less than three 
miles. Their heights are determined by the measurements of the long and sharply-defined shadows that are 
cast from them. 

Forming the north-west border of the same sea, and therefore lying at right angles to the Apennines, is 
a smaller chain called the Alps. Like the Apennines, the Alps have their steepest side facing the Sea of 
Showers. In character this beautiful range is exceedingly rugged, its highest peak. Mount Blanc, rising to 
an altitude of about two and a-half miles. Its most striking feature, however, is the gap in it produced b}' 
what is known as the Great Alpine Valley, which, dividing the chain near the centre, extends to a distance of 
about eighty miles. The bottom of this valley when examined under high telescopic powers, is so extra- 
ordinarily flat, that it appears more like some engineering work than the production of Nature. This 
smoothness is evidently the result of long-continued water action, which had the effect of partly wearing 
down the rugged places, and partly filling up the irregularities with mud and sand; for when the lunar 
oceans were as active as our own are at present, this valley must have been filled \\dth water, and would then 
simply be a strait connecting the two seas. 

The highest of the mountain peaks in the ranges above-mentioned do not exceed four miles; but these 
are not by any means the highest mountains of the moon, for several of the lunar mountains attain an altitude 
of over five miles. Accordingly, the lunar mountains are, in comparison with the diameter of the globe, 
considerably more elevated than the terrestrial mountains. The highest mountain peak on earth has au 
altitude above the sea-level of about five and a-half miles, or nearly the same as the highest mountain on 
the moon. As the diameter of the lunar globe, however, is only one-fourth that of the earth, a distance of 
five miles on the moon represents about twenty miles on earth ; so that it may be said the mountains of the 
moon are five times more elevated above the level of the lunar plains than those on our globe above the level 
of the sea. 

THE CKATERS. 

The numerous white spots indicated in the photographs (see Frontispiece) are, for the most part, higli 
ringed mountain peaks, or craters, as they are termed. The most favourable time for viewing these interest- 
ing objects is when the terminator, or boundary between the light and dark part, passes near them, because 
when seen in this position the sun is low down on their horizon, and consequently each elevated portion of the 
surface casts a long shadow, which has the effect of rendering visible a good deal of detail, impossible to detect 



78 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



on other occasions. The craters are of all sizes, from over 100 miles in diameter down to the smallest objects 
visible with the most powerful telescopes, or to about one mile in breadth. Their number is exceedingly 
great, for upwards of 33,000 are indicated on lunar charts. As this, however, only represents about one-half 
of the entire lunar surface, the actual number on the moon cannot be reckoned less than 100,000. 

These cup-shaped mountains are divided into two classes — viz., craters with central peaks, and those 
with flat bottoms, or, as they are called, walled plains. The craters proper are generally very deep, their 
terraced walls not unfrequently rising from the floor of the crater to a height of over three miles. The walled 
plains, on the other hand, are comparatively shallow, and, unlike the craters, have very smooth and level floors. 
One of the finest specimens of a lunar crater is seen near the southern portion of the moon. It is called Tycho 
(see Plate 17). The diameter of this magnificent crater is no less than fifty-four miles; while its depth is nearly 
three miles. In its centre is situated a high conical hill, 6000 feet in altitude. From the character of the 
surrounding region, one is led to believe that in the days of lunar activity, this large crater was the centre of 
some of the most tremendous volcanic disturbances which ever convulsed the lunar globe. In addition to 
thousands of craters of all sizes, there radiates from its base in every direction a wonderful system of bright 
streaks, some of which are so long that they actually extend to the northern side of the Sea of Serenity. 
These rays are evidently the outcome of some mighty force, generated at a time when the moon was rapidly 
approaching the solid condition. They are, in fact, believed to be huge cracks produced by the contraction of 
the surface of the lunar globe, at a time when the matter of the interior had not yet solidified; for, as 
observation has revealed, the molten substance seems to have flowed out of the rents, thus keeping the 
surface at nearly the same level, but giving it a different colour. 

Copernicus is another gigantic crater, whose diameter amounts to over fifty-six miles, while its terraced 
walls do not attain a greater altitude than about two miles. The central peak of this grand crater terminates 
in six points, the highest of which reaches a height of half-a-mile. Copernicus, like Tycho, is the centre of 
a bright ray system, but it does not extend to so great a distance as that radiating from Tycho, and is probably 
a much later production. 

The walled plains were doubtless at one time large craters, whose bottoms have by some means become 
partly filled up. One of the finest examples of this type of crater is situated at the northern end of the great 
Alpine range, and known as Plato. This plain has a diameter of about sixty miles, while its circular walls vary 
in height from 1| to f of a mile. This class of craters is probably the result of volcanic action. As 
in the case of the ordinary craters, the walls have likely been formed by repeated upheavals of lava and 
ashes ; but, when the force became enfeebled, instead of continuing the ejection of the same material, and 
gradually building up a conical mountain, as in the case of Tycho and Copernicus, molten lava seems to have 
flowed in from beneath, and converted the crater into a smooth plain with greatly elevated walls. The origin 
of the lunar craters has thus, in all probability, been the same as the craters on earth. The lunar craters, 
however, are formed on a more gigantic scale, as might be expected from the great difference that exists 
between the volumes and masses of the two globes. As already mentioned, the force of surface-gravity on 
the moon is but one-sixth of that of the earth ; so that a force which on earth would send a projectile to a 
distance of a mile, would, on the moon, throw the same object to a distance of six miles. Accordingly, the 
volcanic force which produced some of the older terrestrial craters, was, on the moon, sufiicient to build up a 
crater with a diameter six times greater, or, in many instances, with a diameter of over sixty miles. 

The craters on the lunar surface do not at present show signs of the least activity, as the forces of which 
they are the outcome have long since ceased. This shows that the moon, though smaller than the earth, 
is yet older in the scale of development. Being the smaller globe, she would of course cool more rapidly, 
and reach the solid condition long before our earth. In fact, from its size and composition, the moon 
must have cooled down in one-sixth of the time occupied by our globe, and is accordingly this amount further 
advanced in its life's history. If, then, the earth 5^nd moon were i» the same condition with regard to temper- 



Lunar craters— Plate 17. 




Copernicus 





'"-^^^~i&?i^::'i.L£ 



Plato. 



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LUNAK ELEMENTS. 





d. 


h. m. s. 


Synodical Eevolution, ...... 


29 


12 44 2-684 


Sidereal Eevolution, ...... 


.27 


7 43 11-545 


Tropical Eevolution, . . . . 


.27 


7 43 4-68 


Anomalistic Eevolution, ..... 


27 


13 18 37-44 


Xodical Eevolution, ...... 


... 27 


5 5 35-81 


Mean distance from the earth (radius of earth equal to 1), 




. 60-2634 


Mean distance in miles, ..... 




. 238,818 


Maximum distance in miles, ..... 




. 252,948 


Minimum distance in miles, ..... 




. 221,593 


Mean angular diameter, ..... 




31' 8" -00 


Maximum do., 




33' 33" -20 


Minimum do., . 




29' 23"-65 


Actual diameter in miles, ..... 




. 2163-1 


Moon's surface in square miles, .... 




14,600,000 


Do. do. do. compared with the earth's as 1, 




. 0-0742 


Moon's volume „ ,, „ 




0-02033, or ^V 


Moon's mass " „ ,, ,, 




0-01228, or ^ 


Density (compared with water as 1), . 




3-444 


Do. (compared with the earth's as 1), 




0-604 


Surface gravity ( „ „),... 




0-165, or ^. 


Bodies fall iu one second of time, . . . ^ 




. 2-65 feet 


Mean horizontal equatorial parallax, 




0° 57' 2"-7 


Maximum do. do., . 




r 1' 28"-8 


Minimum do. do., . 




0° 53' 51"-5 


Mean eccentricity of orbit, ..... 




. 0-054908 


Inclination of axis to Ecliptic, ..... 




87° 57' 21" 


Inclination of Equator to Ecliptic, .... 




r 32' 9" 


Mean inclination of axis to Ecliptic, .... 




5° 8' 0" 


Maximum libration in longitude, .... 




7° 45' 0" 


Maximum libration in latitude, .... 




6° 44' 0" 


Maximum diurnal libration, ..... 




r r 29" 


Surface of moon never seen, ..... 




0-41 


Surface of moon seen at one time or another, . 




0-59 


Mean revolution of nodes (retrograde) in years. 




. 18-5997 


Mean revolution of perigee (direct) in years. 




8-85 



80 



TEE MOON. 8l 



ature 100 millions of years ago (a period which is not by any means too long), then the moon would reach our 
globe's present condition 83 millions of years ago, which informs us that at the time many of the gigantic 
craters were being formed on the surface of our satellite, the earth was so hot that no terrestrial life whatever 
could have existed. In like manner, if the moon has taken 100 millions of years to reach her present stage, 
then she represents the appearance of our globe far in the future — say 500 millions of years hence. 

The moon, then, has lived her life as a planet, as there is not at present the slightest sign of water or 
moisture of any kind. Neither has she now any atmosphere surrounding her, as proved, not only from the 
blackness and sharpness of the shadows cast by the lunar mountains, but the most delicate tests have been 
applied again and again without the presence of even the smallest quantity of air being detected. The moon, 
therefore, cannot be the abode of life — at all events, life similar to that which exists on earth. At one period, 
however, of her history, vegetable and possibly animal life of some kind may have existed there. Before the 
telescope was invented, and even after it had revealed the fact that there was no water on her surface, the 
moon was believed by many to be a miniature of our earth — a globe teeming with countless forms of life. 
With increase of telescopic power, however, this delusion was dissipated, and the moon accordingly shown to 
be a lifeless world — a world which truly represents the future of our earth; for, by her present appearance, she 
points into the future, and tells us that a time shall certainly come when our globe shall be in very much the 
same condition as herself, when it shall journey round the great centre of the system like the moon at present — 
viz., a barren and lifeless mass, without air or water on its surface. 



CHAPTER VIII. 

ECLIPSES. 

"The moon 
In dim eclipse disastrous twilight sheds 
On half the nations, and with fear of change 
Perplexes monarchs." — Milton. 

In the above lines the author of " Paradise Lost " truly expresses the effect produced in superstitious ages by 
the eclipsing of the two most important heavenly bodies, the sun and moon. When the beautiful " Queen of 
Night " became darkened and " turned to blood," monarchs were in very deed perplexed, and nations seized 
with fear. Being it was believed, the effect of Divine wrath, it was thought that nothing short of rigidly 
performing certain propitiatory acts could prevent the evil that was sure to follow the occurrence of this 
startling phenomenon. The disappearance of the orb of day, as might be expected, produced even a 
greater effect on ignorant minds, especially at the time when the sun was worshipped as a deity. History is 
full of instances of this kind. Nicias, the Athenian general, 400 B.C., was so frightened by an eclipse of the 
moon that he delayed the retreat of his army from Sicily until it was too late to do so successfully, and from 
the opportunity thus missed, his army was destroyed, and he himself perished — a misfortune which was the 
commencement of the downfall of Athens. Columbus, on the other hand, knowing the terror produced on 
ignorant minds by eclipses, used the prediction of one for the purpose of obtaining food supplies for his 
soldiers — a historical fact which has been often employed by modern novelists. Being dependent, while in 
America, on gifts from the Indians for the supply of food, he had on one occasion to give out that he would 
deprive the world of the moon's light if the supply were stopped. The Indians at first laughed at his 
announcement, and continued to refuse compliance with his demands ; but when the eclipse com- 
menced, they were seized with terror, and soon returned to Columbus, bringing with them the accustomed 
tribute.* 

This great fear and disquietude which eclipses of the sun and moon caused in ignorant and superstitious 
ages, was beneficial in this respect, they were carefully recorded, and these records laid the foundation for 
establishing exact science. Posterity was thus enabled to apply to observations those of former generations, 
and the knowledge thus brought together was the means of ultimately revealing the true nature of the 
heavenly bodies, and the nature and cause of the celestial motions. At first even the more advanced in 
thought among the ancients were unable to account for these most startling celestial phenomena, but after 
numerous generations had observed and recorded, the movements of the two orbs were so far understood, that 
the occurrence of eclipses could be predicted with approximate accuracy. In fact, centuries before our era, the 
philosophers of Egypt, Chaldea, and Greece had so carefully studied the motions of the sun and moon as to 
possess a more accurate knowledge of eclipses than the majority of present-day men of average education. It 

* This eclipse took place on the 1st of March. 1.504 — an astronomical fact which has been verified . by modern 
calculations. 
82 



SOLAR ECLIPSES TILL 1900. 



DATE. 


Nature of Eclipse. 


LOCALITY WHERE VISIBLE AND CENTRAL. 




1882. 


May 17, 


Total, 


Northern Africa, Arabia, and Central Asia. 




)) 


November 11, 


Annular, 


Australia and New Zealand. 




1883. 


May 6, 


Total, 


Southern Pacific and New Zealand. 




>> 


October 30, 


Annular, 


Japan and North Pacific. 




1884. 


April 25, 


Partial, 


Cape Colony and Southern Atlantic. 




>> 


October 18, 


» 


Eastern Siberia and Alaska. 




1885. 


March 16, 


Annular, 


North Pacific Ocean and Greenland. 




>> 


September 8, 


Total, 


Australia and New Zealand. 




1886. 


March 5, 


Annular, 


Central America and ]\lexico. 




» 


August 29, 


Total, 


Isthmus of Panama to the Congo and Madagascar. 




1887. 


February 22, 


Annular, 


Southern Pacific. 




5) 


August 10, 


Total, 


Russia. 




1888. 


February 1 1 , 


Partial, 


The Arctic Regions. 




» 


July 9, 


» 


The Antarctic Regions. 




)» 


August 7, 


)> 


(Exceedingly small). 




1889. 


January 1 , 


Total, 


California. 




>> 


June 28, 


Annular, 


Madagascar. 




jj 


December 2, 


Total, 


St. Helena and Central Africa. 




1890. 


June 17, 


Annular, 


Southern China to Tunis. 




)> 


December 12, 


Total, 


Southern Pacific and Australia. 




1891. 


June 6, 


5) 


Arctic Regions. 




>) 


December 1, 


Partial, 


(Exceedingly small), 




1892. 


April 26, 


Total, 


Antarctic Regions. 




)) 


October 20, 


Partial, 


(Exceedingly small). 




1893. 


April 16, 


Total, 


Brazil. 




)> 


October 9, 


Annular, 


Central Pacific. 




1894. 


April 6, 


Total, 


China. 




)) 


September 29, 


)> 


Sumatra, India, &c. 




1895. 


March 26, 


Partial, 


Europe. 




9) 


August 20, 


») 


Asia. 




>) 


September 29, 


Total, 


Sumatra. 




1896. 


February 1 3, 


Annular, 


Southern Pacific. 




)> 


August 9, 


Total, 


Norway and Siberia. 




1897. 


February 1 , 


Annular, 


South America. 




)J 


July 29, 


)) 


West India Islands. 




1898. 


January 22, 


Total, 


Africa, India, China, &c. 




JJ 


July 18, 


Annular, 


Pacific Ocean. 




)) 


December 13, 


Partial, 


(Exceedingly small). 




1899. 


January 1 1 , 


» 


Asia. 




>> 


June 8, 


)) 


Europe. 




>> 


December 3, 


Annular, 


Antarctic Regions. 




1900. 


May 28, 


Total, 


United States and Spain. 




)> 


November 22, 


Annular, 


^ladagascar. 



83 



LUNAR ECLIPSES TILL 1900. 



DATE. 


Nature of Eclipse. 


LOCALITY WHERE VISIBLE AND CENTRAL. 


1882. 






No Eclipses. 


1883. 


April 22, 


Partial, 


New Zealand and Australia. 


)) 


October 15, 


JJ 


North and South America and China, 


1884. 


April 10, 


Total, 


China and the Pacific Ocean. 


V 


October 4, 


n 


Europe, Africa, and America. 


1885. 


March 30, 


Partial, 


China, Japan, and Australia. 


5) 


September 24, 


>5 


Mexico, California, &c. 


1886. 




... 


No Eclipses. 


1887. 


February 8, 


Partial, 


Sandwich Islands. 


>) 


August 3, 


)> 


Madagascar. 


1888. 


January 28, 


Total, 


Central Africa. 


J) 


July 23, 


)) 


The southern part of South America. 


1889. 


January 17, 


Partial, 


Central America and West India Islands. 


)J 


July 12, 


)> 


Madagascar. 


1890. 


June 3, 


!J 


Pacific Ocean. 


)> 


November 26, 


)> 


Pacific Ocean and Philippine Islands. 


1891. 


May 23, 


Total, 


Indian Ocean. 


)) 


November 16, 


)> 


Soudan and Arabia. 


1892. 


May 11, 


Partial, 


Central Africa. 


!> 


November 4, 


Total, 


China. 


1893. 






No Eclipses. 


1894. 


March 21, 


Partial, 


Sandwich Islands. 


»5 


September 15, 


)5 


Brazil. 


1895. 


March 11, 


Total, 


The northern part of South America. . 


>) 


September 4, 


)) 


Peru, &c. 


1896. 


February 28, 


Partial, 


Arabia. 


)> 


August 23, 


)) 


Peru, &c. 


1897. 






No Eclipses. 


1898. 


January 8, 


Partial, 


Africa. 


)J 


July 3, 


)) 


Central Africa. 


J) 


December 27, 


Total, 


Northern Africa. 


1899. 


June 23, 


H 


New Guinea. 


>i 


December 17, 


>) 


Senegal. 


1900. 




... 


No Eclipses. 



84 



ECLIPSES. 85 



was from this knowledge that the astrologers of old derived not a little of their power, for heing able to give 
information of their occurrence, astrologers only were considered capable of interpreting the meaning attached 
to their occurrence. 

Though enabled to roughly predict the occurrence of an eclipse, the astronomer of old did not do so from 
the modern method of calculation, but solely from the discovery he had made, that, with certain modifications, 
the same eclipse occurred after regular intervals. This remarkable period is called the Saros, or Metonic cycle. 
Its length was found to be eleven days longer than eighteen years. If, therefore, an eclipse occurred, it was 
known that it would be again seen after that interval. The eclipse, however, might not be again 
witnessed in the same locality, as the period more accurately consists of 6585'32 days. Accordingly, when the 
same eclipse once more occurs, it does not take place till one-third of a day, or eight hours, later than the time 
at which it before happened, and the magnitude of the eclipse is also different. The sun and moon may, 
therefore, when eclipsed eighteen years afterwards, be beneath the horizon, and the phenomenon be invisible 
at the place from which it was formerly seen — a consequence which must have greatly increased the difficulty of 
discovering the Saros, and which gives us an idea of the length of time that doubtless elapsed before it was 
detected. In this period no less than seventy eclipses usually take place, forty-one of which are solar, and 
twenty-nine lunar. The Tables on pages 83 and 84 contain the different eclipses occurring in the Saros which 
ends with the present century. 

ECLIPSE SEASONS. 

Those who first discovered the Saros would doubtless be unable to account for it, and it was only when 
the movements of the sun and moon were clearly understood that the cause of eclipses recurring in regular 
periods became known. The period, in fact, depends entirely on the connection which exists between the 
motions of the sun, moon, and nodes of the lunar orbit. As mentioned in Chapter VII., the nodes of the moon's 
path revolve round the ecliptic in a retrograde direction, in an interval of about eighteen and a-half years. 
This has the effect of shortening the intervals of successive conjunctions between the nodes and the sun and 
moon. If, therefore, the shadow of the earth be in conjunction with a node, it will be so again after travelling 
nearly round the heavens, not in a year's interval, as it would be if the node were stationary, but, from its 
regression, in a period of 34G'62 days. This is called an eclipse year, and nineteen of these are equal to 
6585*78 days. Now, as we have already seen, the length of a lunation, or the interval between two conjunc- 
tions of the sun and moon, is 29'5306 days, which being multiplied by 223 gives 6585-32 days — a difference of 
only 0'46 of a day. Accordingly, after 223 conjunctions of the moon with the sun, the two orbs will once more 
be in a line with the nodes, as during the interval the nodes have journeyed nearly round the heavens, and an 
eclipse will again take place. It will, however, be slightly different in appearance from the former one, when 
the sun and moon were in the same position, as during the difference between the two periods mentioned 
above (0"46 of a day, or about 11 hours), the sun has apparently moved about half a degree to the eastward of 
the node. This has the effect of either increasing or diminishing the magnitude of the eclipse, depending on 
the movement of the sun whether towards or away from the node respectively. In all cases, however, the 
eclipse entirely disappears after it has been repeated a certain number of times. In lunar eclipses the repetitions 
of the same eclipse are performed regularly every 6 585 "32 days for over 8C5 years ; and the solar eclipses for 1200 
years. At the commencement of the Saros the eclipses of the moon begin as a small partial one, with the sun 
to the east of the node about twelve degi-ees. At each successive occurrence the magnitude of the eclipse 
increases, till after fourteen repetitions the sun generally arrives so near the line of nodes that the eclipse 
becomes total. As the diameter of the shadow of the earth, where cut by the lunar orbit, is between two and 
three times greater than the diameter of the lunar disc, it occupies twenty-two repetitions of the Saros before 
the moon begins to emerge from the shadow, or all of these eclipses are total. By tliis time the sun has 
travelled to the west of the node, and before the eclipse fails to appear, thirteen partial occurrences generally take 
place. The period in which the same solar eclipse is repeated being longer than the lunar one, no less than 

M 



86 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



seventy sometimes occur. Of these, forty-five are visible either as total or annular eclipses, the remaining 
twenty-five being partial. 

From what has already been stated, it will be supposed that it is only when near the nodes that the sun 
and moon can be eclipsed. This is indeed the case, as at other times the moon is so far above or below the 
plane in which the earth moves, that an eclipse is impossible. If the moon travelled round our globe in the 
same level as that in which the sun and earth are situated, the sun and moon would be eclipsed once every 
month — the former at the time of new moon, by the lunar globe coming exactly between us and the solar 
disc ; the latter at the time of full moon, by the lunar globe passing through the shadow of the earth. The 
path of the moon, however, as mentioned in Chapter VII., is not thus situated, but inclined to the plane of the 
earth's orbit, or to the plane of the ecliptic, at an angle of over five degrees. Accordingly, it is only when the 
moon is within a certain distance from this plane that an eclipse can be produced, so that instead of twenty- 
five eclipses taking place every year, as there would be if the plane of the lunar orbit coincided with that of 
the earth, only three or four usually occur. 

The sun in his apparent movement round the heavens passes the ascending and descending node at 
intervals of about six months, and therefore the eclipses in a year occur in two groups, separated by that 
interval. If the nodes of the lunar orbit were stationary, "the eclipse months" would be exactly half-a-year 
apart, but as the nodes regress, the period is shortened, being equal to five months and twenty days. The 
period in which eclipses may occur are, consequently, earlier every year by double the difference of ten days 
from six months, or by twenty days. The number of eclipses occurring in an eclipse season depends on the 
manner in which the conjunction with the node takes place. If, for example, the new moon took place when 
the lunar globe was exactly at a node, a central eclipse of the sun would be the result ; while half-a-month 
before and after this event, at the time of full moon, the moon, though being near the opposite node, would yet 
be sufficiently distant from it as to escape being eclipsed. Under such circumstances only one solar eclipse 
would take place — the minimum number in an eclipse season. If, on the other hand, the moon should 
be exactly in the node at the time of opposition to the sun, or at full moon, a central lunar eclipse 
would be produced; and half a lunation later or earlier, at the times of the preceding and following new moons, 
the lunar globe would be within sufficient distance of the node to partially eclipse the sun. This is the 
greatest number of eclipses that can occur in an eclipse season — viz., two solar and one lunar. The maximum 
number of eclipses occurring in a year is six, two of which are lunar, and four solar. Occasionally there may 
be seven eclipses, but usually the number does not exceed four or five. 

Although generally the solar eclipses exceed in number those of the moon in the proportion of three to two, 
yet from a given point on the earth's surface more lunar eclipses than solar are seen. This is owing to the fact that 
solar eclipses are only visible from very limited portions of our globe, while eclipses of the moon, which do not 
depend on the lunar parallax, can be seen over considerably more than a complete hemisphere ; so that the 
proportion of lunar and solar eclipses witnessed from a given place is more than reversed. Eclipses of the 
sun and moon are of great use in chronology, as by them many distant dates have been accurately recovered. 
Ptolemy records many eclipses, and gives the reigning monarch at the place where observed, from which, by 
verification, a number of valuable points in Egyptian, Babylonian, and Grecian chronology have with precision 
been established. 

ECLIPSES OF THE MOON. 

From what has been stated it will be seen that it is only at the time of full moon, and when the limai 
globe is then within a certain distance from one of its nodes, that the moon can be immersed in the shadow 
of the earth, and become obscured or eclipsed. This distance is not always the same, as it obviously depends 
on the inclination of the lunar orbit, and the breadth of the earth's shadow, both of which are subject to 
variation. As already mentioned, the inclination of the moon's path to the plane of the ecliptic varies from 
5 degrees 13 minutes to 5 degrees 3 minutes. The breadth of the shadow cone where cut by the lunar orbit 



TH E 



Total Lunar Eclipse 

OF JANUARY 28th, 1888, 

As Bl'.otographcd at Murrayfield Observatory by \V. Peck, F.R.A.S., 
with Silver-on-Glasa Reflecting Telescope of 13 inohea aperture. 

THE FOLLOWING ABE ACCORDING TO GREENWICH TIME: — 




9h, 32m. Os. 




TOh Om 20s. 




9h. 37m 40s. 




IOh ^5:^ 5s. 




9h. 45m, 203. 




12h. 36m. 37&. 




12h 47m 20s 




13h. 1m 38s, 




13 I 7m. 20 



ECLIPSES. 



87 



alters to even a greater extent, as it depends not only on the varying distance of the earth from the sun, hut 
also on the varying distance of the moon from the earth. From these causes the distance of the moon from 
the node in order to be eclipsed, or the " lunar ecliptic limits " as it is called, alters from 12 degrees 5 minutes 
to 9 degrees 30 minutes. If, therefore, the moon be within the greater of these limits from one of the nodes 
at the time of full moon, it may be eclipsed, and if nearer the node than the smaller limit it will certainly 
come into contact with the earth's shadow. As the sun apparently journeys round the star-sphere at the 
average velocity of about one degree per day, it follows that an eclipse of the moon cannot take place if the 
full moon occurs more than thirteen days before or after the time of the sun's conjunction with the node. 

When in January the earth is nearest to the sun, the shadow is shortest, and when in the opposite part of 
her orbit, in July, it is longest ; while midway between these positions it extends from our globe to the average 
distance of 857,000 miles. Accordingly, if the moon revolved round our globe in a circular path, the duration 
of the eclipse, which depends on the breadth of the shadow cone, would vary with the season of the year. But 
the moon, as we have seen, travels in an orbit which is elliptical, and, consequently, her distance from our 
globe alters to a considerable extent. Owing to this variation of distance, the breadth of the shadow, where 
traversed by the moon when totally and centrally eclipsed, is sometimes as much as three times the diameter 
of the lunar globe, and at other times scarcely more than twice its size. In calculating lunar eclipses, 
astronomers do not compute the breadth of the shadow in miles, but its apparent angular breadth as viewed 
from the earth. The following are the different diameters of the terrestrial shadow, at the place where it is 
cut by the lunar orbit, or the angle C D, Fig. 1, Plate 18, for various positions of the sun and moon : — 

APPARENT DIAMETER OF THE EARTH'S SHADOW IN LUNAR ECLIPSES. 



POSITION OF SUN. 



Nearest to the earth, 



At mean distance from the earth, 



Farthest from the earth, 



POSITION OF MOON. 



Farthest from the eartli, . 

At mean distance from the earth. 

Nearest to the earth, 

Farthest from the earth, . 

At mean distance from the earth, 

Nearest to the earth, 

Farthest from the earth, . 

At mean distance from the earth, 

Nearest to the earth, 



APPAHENT DIAMETER OF SHADOW. 



1 "^ 


15' 


24" 


]° 


23' 


2" 


1 ° 


30' 


40" 


r 


15' 


58" 


1° 


23' 


35" 


1° 


31' 


13" 


r 


16' 


28" 


1 


24' 


6" 



V 31' 44" 



In consequence of this variation in the breadth of the terrestrial shadow, at the place where traversed by 
the moon, the duration of total central eclipses is of different lengths. The greatest period of totality lasts 
about two hours, and as the moon moves over her own diameter in an hour, the whole interval, from first to 
last contact, is thus about four hours. The length of a partial lunar eclipse depends, of course, on the 
distance of the moon from the node, it being least when near the ecliptic limit. 

When the moon has been wholly immersed in the shadow of the earth, she is not, as one might suppose, 
invisible, but generally shines with a dull, copper-coloured light. This visibility is caused by the atmosphere 
of the earth refracting the solar rays into the dark shadow, and faintly illuminating the lunar disc. The blood- 
red colour that the moon sometimes assumes is the outcome of the effect which the lower portion of the atmo- 
sphere has on the light rays, for by it the blue rays are absorbed, and the red only pass through. As the 



88 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



horizontal refraction amounts to over half-a-degree, and as the diameter of the terrestrial shadow is more than 
one degree, the moon is thus, even when in the centre of the shadow, slightly illuminated (see Plate 18). 
There are instances, however, of the moon completely disappearing during the total phase, these having been 
brought about by dense clouds in the terrestrial atmosphere. The appearance of the lunar disc when 
immersed in the shadow of the earth is, therefore, an index of the condition of our atmosphere at those places 
on the edges of the earth's disc through which the light is passing at the time. If, for instance, the moon 
appears bright, the sky is clear and the weather fine at those places where the sun is rising and setting ; if, on 
the other hand, she is scarcely visible, or entirely disappears, the weather is stormy. 

In Fig. 1, Plate IS, a faint shadow, or penumbra as it is called, is indicated. This, however, cannot be 
seen on the moon, though the time of the lunar globe in entering and leaving it is always given in the 
almanac. Within the penumbra lines indicated in the Plate, the moon is only partially illuminated by the 
sun, as, until the moon has travelled outside of the penumbra, part of the solar disc, as seen from the moon, is 
hidden by the earth. But even when nearly all of the sun is cut off by the earth at the time when the lunar 
disc is either about to enter or leave the umbra, or dark shadow, the moon appears to shine with her usual 
brightness, owing to the great contrast between the nearly total obscuration, when immersed in the shadow, 
and the partial illumination from the sun's direct rays. 

ECLIPSES OF THE SUN. 

As already mentioned, the sua is always eclipsed when the moon is in conjunction with him at the time 
she is within a certain distance from either of the nodes of her path. This distance from a node within which 
the sun is eclipsed, is termed the " solar ecliptic limits." These are larger than the lunar limits, because the 
parallax of the moon has the effect of increasing them to a considerable extent. If viewed from the centre of 
the earth, for instance, the sun would often be entirely free from the lunar disc, while from certain parts of the 
surface of our globe, the" moon, from the effect of parallax, may be so much depressed or raised, that an eclipse 
of considerable magnitude will be seen. The major solar ecliptic limit is accordingly as great as 18 degrees 
31 minutes, within which distance from a node, the moon, in passing the sun, may produce an eclipse. The 
minor limit is 15 degrees 21 minutes, within which distance from a node, the moon, in coming into conjunc- 
tion, will certainly eclipse the sun. But, while under these conditions a solar eclipse of some kind will be 
produced, it may not necessarily be a central eclipse. In order to insure that the moon will be seen from 
some part of our globe centrally projected on the sun, she must be nearer to the node than the distances above 
stated. Before a central solar eclipse can be produced, the moon must, in fact, be within about 10 degrees of 
the node of her orbit at the time of conjunction with the sun. 

Owing to the variation of the moon's distance from the earth and sun, the length of the lunar shadow is 
not always the same. It alters in the proportion of about 87 to 84, or, in actual miles, from 236,000 to 228,000. 
As this latter distance is less than the moon's distance from the earth, it follows that sometimes the lunar 
shadow does not touch the surface of our globe at all, but falls short of it by a considerable distance. The 
different distances of the vertex of the lunar shadow from the earth for various positions of the moon and sun 
are given on the Table on page 89. 

It is only in those cases where the length of the lunar shadow is greater than the distance of our satellite 
from the earth that the sun can be totally eclipsed. On all other occasions, when the shadow is shorter than 
the distance of the moon, the eclipse, though central, is not total. The diameter of the lunar disc is then 
slightly smaller than that of the sun, and consequently the solar disc is not completely hidden, but appears as 
a ring of light surrounding the dark globe of the moon. This is called an annular eclipse of the sun, and, as 
might be expected, this phase occurs more frequently than the total one ; they do so, in fact, in the proportion 
of about three to two. 

In the case of total eclipses, the breadth of the shadow cone, where it falls on the surface of the earth, is 
not very great, being under the most favourable conditions only 167 miles in diameter (see Plate 18). This 



Eclipses— Plate 1$. 




ECLIPSES. 



shadow spot, however, travels over the surface of our globe at a considerable velocity, and consequently the 
total phase is not confined to so limited a region, but may be seen at places differing from each other by 
distances often amounting to thousands of miles. If the earth had no rotation, and the moon -were situated 
on the equator, the velocity of the shadow over the terrestrial surface would be the same as that of the rnoon in 
her orbit — viz., 2100 miles an hour. The earth, however, is rotating in the same direction as that in which the 
moon travels in her orbit, and therefore the movement of the shadow is retarded by the rotation velocity of 
the place on which the shadow falls. Accordingly, when the shadow of the moon falls on the equatorial regions 
of our globe, it journeys at the velocity of 1060 miles an hour.* This is its slowest speed, as places near the 
equator are carried eastward by the rotation of the earth at the maximum velocity, or about 1040 miles an 
hour, yet it is equal to the speed of a cannon ball. As the locality at which the total eclipse is.visible increases 
in distance from the equator, the speed of the shadow becomes greater, until the shadow falls beyond 
the pole. The rotation velocity of the place then being in the same direction as the movement of the 
shadow, it becomes added to it, and the speed of the shadow is at a maximum. 

Along with this variation of the velocity of the lunar shadow in traversing the surface of our globe, the 
duration of the total phase also varies with the place of observation. As the movement of the moon in her 

DISTANCES OF VERTEX OF LUNAR SHADOW FROM THE EARTH IN SOLAR ECLIPSES. 



POSITION OF SUN. 


POSITION OF MOON. 


POSITION OF VERTEX OF SHADOW. 


Nearest to the earth . 

>j - • 

Farthest from the earth 
J) • 


In apogee, .... 

At mean distance, 

In perigee, .... 

In apogee, .... 

At mean distance, 

In perigee, .... 


1 

23,000 miles in front of the earth. 
9,000 „ from the earth. 
8,000 „ behind „ 

16,000 „ from the earth. 

2,000 „ „ 
16,000 „ beyond „ 



orbit is apparently most retarded near the equator, the length of the total phase is there longest. It 
is not, however, of long duration, for under the most favourable conditions it only lasts 7 minutes 53 
seconds. As the latitude of the place increases the duration of total phase becomes less ; at the latitude of 
London it is not greater than 6 minutes. Annular eclipses, as already mentioned, take place when the lunar 
shadow fails to reach the surface of the earth. They are, therefore, greatest, or the ring of light broadest, 
when the sun is nearest the earth and the moon in apogee ; under these conditions the apparent diameter 
of the sun is at a maximum, and the lunar disc smallest. Then also the moon moves at her least velocity, 
and consequently the duration of the annular phase is greatest ; at the equator it is 12 minutes 24 seconds, 
and at the latitude of London a little less than 10 minutes. 

From all places lying within a certain distance to the north or south of the line where the sun is 
centrally eclipsed, a portion only of the solar disc is obscured. This distance on the surface of the earth from 
the line of central phase is determined by the penumbral lines E F (Fig. 2, Plate IS). Within these the 
sun is partially eclipsed, the amount of obscuration increasing with the approach to the line of central phase. 
On some occasions the penumbral lines are no less than 4400 miles apart, so that while total and annular 
eclipses can only be seen within very narrow limits, the same eclipse will be visible as a partial one every- 
Avhere within 2000, and sometimes 3000 miles of the shadow path. 

* =2100 miles (velocity of moon in orbit) - 1040 (rotation speed of equator) = 1060. 



CHAPTER IX. 

ASTRONOMICAL INSTRUMENTS. 

" Here truths sublime, and sacred science charm, 
Creative arts new faculties supply, 
Mechanic powers give more than giant's arm, 
And piercing optics more than eagle's eye." — Beattie. 

INSTRUMENTS OF THE ANCIENTS. 

As soon as primitive man began to take notice of the various celestial phenomena continually occurring, he 
would endeavour to find out how such remarkable appearances were caused. In order to do this successfully, 
he would soon discover that it was necessary to constantly observe how the different heavenly bodies moved. 
Hence would arise the necessity for employing some kind of instrument, and such an instrument Nature 
supplied to him when dwelling on the level plains of eastern countries, by giving him a clear and regular 
horizon. This was probably the first astronomical instrument. By it the rising and setting of the 
various orbs would, with tolerable accuracy, be determined, and also their apparent distances from each other 
indicated. Combined with these horizontal observations, records of eclipses, and conjunctions of the planets 
with the brighter stars lying near their paths, and with each other, would be carefully made. The Egyptians, 
Chaldeans, and Chinese made thousands of such observations hundreds of years before our era, and by means 
of them discovered so important a period as the Saros. From these observations, too, it would be found that 
some kind of instrument was necessary for determining the position of the heavenly body when above the 
horizon, and this want would lead to the invention of the first angular instrument — viz., the gnomon. 

The sun, moon, and stars, it would be noticed, after appearing above the horizon, would mount into the 
sky, gradually increasing their altitude, till reaching a certain height, when they would begin slowly to fall and 
approach the horizon again towards the west. The points in the sky where the various orbs attained their 
highest altitude would soon be discovered to be all situated on a single line —a line which accurately divided 
the diurnal course of each orb into halves. Accordingly, the" position which the different bodies occupied 
when on this line, now known as the meridian, would be considered as important, and means would be required 
to obtain the information. In the case of the sun and moon, this was easily done by determining the lengths 
of the shadows cast by these luminaries, and, consequently, for many generations the altitudes of the stars 
could not be measured. The first astronomical instrument might simply be an erect staff, whose 
height was known. The invention of the gnomon is attributed by Herodotus to the Babylonians ; but it was 
also employed by the Egyptians, Chinese, and Indians. Doubtless the numerous obelisks which have been 
erected in eastern countries were originally put up to serve as gnomons, and even the Pyramid may, at first, 
have been a more advanced kind of instrument for determining both the horizontal and meridional positions of 
heavenly bodies.. 

From the length of the shadow cast by the gnomon the solar and lunar altitudes were determined, and, 
from the equal lengths of the shadow at equal distances from the meridian, the exact direction of that line, and 
90 



ASTRONOMICAL INSTRUMENTS. 91 



the time of the passage of those luminaries across it, were known with approximate accuracy. By observing 
the gradual increase or decrease of the meridional shadow from day to day, the times when it was longest and 
shortest became known. These occasions, which were called solstices because the sun was then found to 
remain for several days at nearly the same altitude, were noticed to occur regularly at certain intervals, 
and by this means the length of the solar year was first approximately known. From the use of the 
gnomon, also, the inclination of the path in which the sun apparently moves round the star-sphere to the 
equator was measured. By such means, the Chinese, 2000 years before our era, found that this inclination, 
or the obliquity of the ecliptic, as it is now termed, was twenty-three degrees thirty-eight minutes (see 
The Earth, Chapter V.). 

Very often the gnomon was constructed of great length, in order to insure accuracy of observation, yet 
notwithstanding this, the results were somewhat inaccurate. The sun, not being a luminous point, but a disc of 
some size, the shadow projected from the end of the gnomon is not sharply defined, but gradually fades away. 
Accordingly, the length of the shadow was not known with certainty, and the greater the gnomon's height 
the greater the difficulty in determining the extremity of the shadow. To obviate this defect, the gnomon 
was sometimes terminated with a disc of metal, pierced with a small hole. This cast an elliptical shadow on 
the ground, with a central luminous spot, the centre of which gave, more accurately than the ordinary gnomon, 
the height of the sun's centre. In comparatively modern times this simple ^ 

astronomical instrument was not altogether unused, for in the year 1467 a ''°% zemtth 

^c^_^— "T — 1 — r~~->^ 

gnomon 277 feet high was erected at Florence, and about the same time one y^^^^T- ~\X 

80 feet in height was erected at Pans. //V \ ^\\ \\ 

Another very ancient instrument for determining the height of the sun r / \\"-.\\ W 

was the hemisphere of Berosus, which consisted of a hollow hemisphere, ^Tr Wtr\\ ] J^ 

with a horizontal rim, with a style placed in its centre. This instrument V\ \ \\\\ / / 

was an advance on the gnomon, and it doubtless led to the invention of \\. ^x^s^Wy 

circular instruments generally. The altitudes of the sun and moon were ^^^<[[ri3^^ 
determined directly by observing the division on which the extremity of 

. P .... Fig. 21. THE MERIDIAN INSTRU- 

the shadow fell ; and this hemisphere was also employed in dividing the jient of eratosthenes. 

day into equal parts. 

We now come to the use of circular instruments properly so called. As far as is known, the 
Alexandrian astronomers under Eratosthenes were the first to employ the circle in making observations, 
but doubtless it had been used long before his time. The observatory at Alexandria had been established 
at least 300 years B.C., and many valuable observations had been made there by the two celebrated 
philosophers, Aristillas and Timocharis. After these came Aristarchus, -sAho must have employed circular 
instruments of some kind, as his observations did much to extend the knowledge of the heavenly 
bodies. Eratosthenes, however, has the honour of inventing the first meridian instrument, which 
consisted of two circles of nearly the same size, and crossing each other at right angles (see Fig. 21). 
The circle S N was placed in the meridian, or exactly north and south, and in such a position that 
the other circle was tilted upwards, so as to point to the celestial equator. By this means the altitude 
of the sun when on the meridian could be conveniently observed, and the exact time of the sun crossing 
the equator, or the instant of the equinox, determined. 

As mentioned in Chapter I., the division of the circle into 360 equal parts doubtless originated 
from the rude discovery that the great circle of the heavens, as marked out by the sun's apparent 
yearly course, consisted of 360 spaces, each of which was traversed by the sun in the interval of 
a day. This supposition is borne out by the fact that the old solar year contained only 3(50 days. 
Hipparchus, about 160 B.C., employed such a division of the circle, and invented many instruments 
and methods of observations on a basis so sure, that for several generations they wore not surpassed. 



92 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 




Fig. 22. the equatorial 
astrolabe. 



One of the most important of his inventions was the celebrated astrolabe {Figs. 22 and 23). This 
consisted of a meridional circle, and several interior circles which could move about an axis. One 

of these, as in the instrument of Eratosthenes, was directed towards 
% zz.HnH *^® equator, while the others, swinging about an axis which pointed 

to the poles of the heavens, were used to determine the distances 
of the various celestial objects from that great circle of the celestial 
sphere. Unlike the instruments hitherto emploj^ed, the object did not 
require to be on the meridian in order to find this position, but its 
equatorial distance, or declination as we now call it, could be measured 
during any time it remained above the horizon. To determine the 
position of a heavenly body with respect to the ecliptic or sun's 
apparent annual path, a similar instrument was devised, only the axis 
round which the circles moved, instead of being fixed, as on the last- 
mentioned instrument, had itself a movement round a second axis. 
This was to enable the observer to make the principal axis coincide 
with the poles of the ecliptic, or those points which are perpendicular 
to the annual path of the sun. As the position of these points with 
respect to the horizon, owing to the diurnal rotation of our globe, is 
constantly altering, the axis of the instrument would thus require to 
be adjusted for every observation. By means of the second axis this 
could easily be done, when the distance of the particular object from 
the ecliptic could be measured. In this way the first accurate star 
catalogue was made by Hipparchus, who determined the positions of over 1000 stars with remarkable accuracy. 
It was by this means that the important discovery of the precession of the equinoxes was made ; for 
by comparison of his own positions of the stars with those made by Aristillus, Hipparchus found that 

the stars were apparently travelling along the ecliptic in an easterly 
direction, or the equinoctial points were moving in the opposite direc- 
tion, to the west {see Chapter II.). 

The next celebrated astronomer after Hipparchus was the so-called 
" Prince of Astronomers," Ptolemy, who made observations at Alexandria 
about the year 150 a.d. He principally employed the instruments 
invented by Hipparchus, but also used another which he specially 
describes — viz., the Parallactic Rules. This instrument is believed to 
have received its name from being employed in determining the 
parallax of the moon. It consisted of three long rods, one of which 
had divisions on it, whereby the angle of the summit of the instru- 
ment was found, which was equal to the zenith distance of the object 
{Fig. 24). This type of instrument was used by astronomers as late as 
the fifteenth and beginning of the sixteenth centuries — a fact which 
shows that it must have been considered capable of measuring angles 
with considerable accuracy. 

Up to this time astronomers could not meet one very great want. 

They could not, even with approximate accuracy, by mechanical means 

determine time. Of course, if the sun were above the horizon, the 

time was easily found by means of the sun-dial, but if the sky were cloudy, or during the night, the 

time was not known with certainty, as the mechanical apparatus for indicating time was very defective. 




Fig. 23. the ecliptic astrolabe. 



ASTRONOMICAL INSTRUMENTS. 



93 



The principal instrument used for this purpose was the clepsydra, or water-clock, which was simply a vessel of 
a particular shape with a small aperture at the bottom through which the water flowed, the time being 
indicated by the height of the water in the vessel, or by the amount which flowed out. The iuventiun 
of this ingenious instrument is attributed to the Egyptians ; but as it could not be relied on for astronomical 
observations, it was not much employed by astronomers. Ptolemy entirely rejected it, and for his more 
important observations accurately fixed the time by measuring the altitude of the sun during the day, and 
during the night by making a similar use of some bright star. 



INSTRUMENTS USED BEFORE THE INVENTION OF THE TELESCOPE. 

From the time of Ptolemy to the beginning of the sixteenth century, little improvement was made in 
astronomical instruments. Till then the best observations had been made in the east, principally by the 
Arabians and Persians. In the country of the latter, towards the end of the thirteenth century, a magnificent 
observatory was erected, the remains of which were discovered in the year 1830. According to the best 
Mohammedan writers, this observatory contained an apparatus for representing the celestial sphere, the signs 
of the zodiac, the conjunctions, transits, and revolutions of the different 
heavenly bodies. Through an aperture in the dome, the solar rays 
were transmitted, and by falling upon certain lines on the paved floor 
indicated the altitude and declination of the sun, and the hour of the 
day. 

Instrumental astronomy in the east reached its height towards the 
middle of the fifteenth century. About the year 1430, the Tartar prmce, 
Ulugh Begh, established at his capital, Samarcand, an academy of 
astronomers, and erected for their use the most magnificent and costly 
instruments. Among these was a gnomon 180 feet in height, by 
means of which the obliquity of the ecliptic was determined to be 
20 degrees 30 minutes, the precession of the equinoxes 1 degree in 
70 years, and the various elements for the construction of tables, 
which have been proved to rival in accuracy those of Tycho. Hitherto 
only one star catalogue had been constructed — viz., that of Hippar- 
cbus ; Ulugh Begh, however, constructed another, and accordingly had 
the honour of producing the second, after an interval of sixteen centuries. 

With the death of Ulugh Begh commenced the decline of astronomy in the east. It was beginning, how- 
ever, to be cultivated among races which were capable of developing the intellectual powers to their fullest 
extent. Europe had by this time awakened from the lethargy in which it had been enveloped for so many ages, 
and astronomy, among other sciences, began to be cultivated with marked success. It was in this condition 
when Copernicus greatly stimulated the study by totally renovating the science. This he accomplished by over- 
throwing the Ptolemaic system, which had for so many centuries held sway, and advancing one of his own, 
which in after times was proved by repeated observations to be accurate. These observations were furnished 
by the celebrated Danish nobleman Tycho Brah^, a believer in the older systems, who afterwards invented 
a system of his own, wherein the earth was still considered to be the centre of the universe. Tycho was an 
indefatigable and skilful observer, and as such was considered to be vastly superior to any who had preceded 
him since the revival of astronomy in Europe. What Hipparchus, the so-called father of astronomy, had been to 
the science of the ancients, Tycho was, to as great an extent, to the science of the middle ages. His observator}', 
which was erected at Huen in the year 1576, was a magnificent building, and was considered to be next iu 

importance to the one established at Alexandria under the Ptolemies. The principal part of this observatory, 

N 







Fig. 24. the parallactic rules. 



94 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



which Tycho called Uraniberg, or the city of the heavens, consisted of a building sixty feet square, with towers 
to the north and south, containing also a museum and library. The collection of instruments at this observa- 
tory was the largest and finest which had ever been made. At first the principal ones employed were similar 
to those invented and used by Hipparchus, except that they were larger and of more accurate construction. 

One of the chief instruments used by Tycho was the equatorial astrolabe, already described as having been 
invented by Hipparchus. With this apparatus Tycho was enabled to determine Avith far greater accuracy 
than had hitherto been done, the declinations and right ascensions of 1500 stars, and this, too, without the aid 
of a clock. One of these instruments was of a very large size, having a circle over seven cubits in diameter, 
which (taking the cubit as eighteen inches in length) is about eleven feet, and was, therefore, probably more 
accurate than the smaller instruments he possessed of the same kind. Another noted instrument was a mural 
quadrant, five cubits in diameter, very minutely graduated ; also a moveable one, by means of which the alti- 
tude and azimuth of an object could by one observation be determined with great accuracy. Another very 
important instrument employed at Uraniberg, and invented by Tycho, was one which only contained a portion of 
a circle, called the sextant. This instrument was greatly used in measuring the angular distance of two heavenly 
bodies from each other, in particular, of the moon from a star. By means of his numerous instruments Tycho 
was able to fix the position of any celestial object to within about fifteen seconds of arc, a considerable advance 
on the observations of Hipparchus, as these latter were not certain to within less than ten minutes ; and it was 
from the accumulation of the numerous observations thus accurately made, that his disciple, . Kepler, was 
supplied with materials by which he may be said to have constructed the true system of the universe. 

THE INVENTION OF THE TELESCOPE. 

The telescope is undoubtedly the most important of all astronomical instruments, giving, it may be said, 
a new sense to the human race, whereby many of Nature's greatest mysteries have been revealed. Like several 
other important inventions the origin of the " optic tube " is lost in obscurity, and like many of them also, it 
was rather the outcome of a particular age than of an individual mind. For some time previous to the com- 
mencement of the fourteenth century lenses were in common use for perfecting vision, a fact which leads one 
to believe that a combination of two or more of them would be made during the long interval that elapsed 
between the knowledge of lenses and the time which has been assigned to the invention of the telescope proper 
— viz., near the middle of the seventeenth century. 

The exact date at which the telescope was invented is not known with certainty. Galileo knew absolutely 
nothing about it till the year 1609, but it is certain that its use was known in Northern Europe some time 
prior to this date. It was only through information casually received that Galileo learned there was such an 
instrument, and, though unable to see one, he soon discovered the principle on which it was constructed. By 
a combination of a large convex and small concave lens fitted into a leaden tube, he contrived an instrument 
which was capable of giving a distinct view of distant objects. The first instrument constructed on this prin- 
ciple magnified only three times, but it was soon superseded by another which magnified eight times. The 
success of these instruments encouraged Galileo to attempt the construction of a larger one, in which he was 
entirely successful, for a telescope was produced magnifying no less than thirty times. By means of this instru- 
ment, one which was not nearly so perfect as a modern pocket telescope, the science of astronomy was greatly 
advanced. Numerous discoveries were soon made with it. Mountains were noticed in the moon, and spots 
on the sun ; Venus was found to have phases, thus proving the truth of the Copernican theory ; Jupiter to 
have satellites ; Saturn to have a strange appendage ; and the Milky Way to be composed of myriads 
of stars. 

In this form of instrument, which is still used as the opera-glass, the rays, as will be noticed from (a) Fig. 25, 
pass through the concave eye-glass before they reach the focus of the large convex lens, where the image of 
the distant object is formed. The Galilean telescope has never been constructed of large dimensions, as it is a 



ASTRONOMICAL INSTRUMENTS. 



95 



very defective instrument for astronomical purposes, owing to the smallness of the field of view and its unsuit- 
ability for measuring the position of objects. 

It was not till after the above great defects of the Galilean telescope had been fully recognised that it 
was suggested by Kepler that an instrument might be constructed with two convex lenses, instead of a convex 
and concave as formerl}^ This valuable idea, however, was not immediately put into practice, for it was not 
till the year 1637 that an instrument of this kind was really made (see (b) Fig. 25). The new telescope 
differed from the Galilean in having the single eye lens outside the focus of the large convex or object lens. 
Accordingly, the small glass was used simply as a kind of microscope to magnify the image already formed by 
the object glass. Huygens further improved this form of instrument by applying an eye-piece consisting of 
two convex lenses, which had the effect of giving a more distinct image than a single lens. 

THE REFKACTING TELESCOPE. 

In order to make the form of telescope proposed by Kepler as perfect as possible, the focus of the object 
lens had to be of a very great length. From the increase of the focal length, the size of the image in the focus 




A Object Glass. 

B Concave Flint Lens. 



Fig. 25. The Refracting Telescope. 

C Concave Eye-piece. 
I) Convex Eye-piece. 



E Modern Achromatic Eye-piece. 
F Focus of Object Glass. 



is also increased, and the smaller the diameter. of the object glass in proportion to the length of focus, the 
more perfect the vision of distant objects. Accordingly, this form of instrument was often constructed of great 
length. In 1672, Campan, of Bologna, made one which was no less than 136 feet long; Huygens one whose 
length was 123 feet, which he presented to the Royal Society of London ; while Ausout possessed one 600 feet 
long, but it was so unwieldy that it could never be used. These extravagant lengths to which refracting 
telescopes at the commencement of the eighteenth century had attained were, as already mentioned, the out- 
come of the attempt to secure a powerful and perfect instrument. This the enormous focal lengths of the 
object lenses proved to be impossible in the refracting telescope. Though by increase of length the defects could 
be somewhat diminished, they were not altogether eliminated. The greatest imperfection was the chromatic 
aberration, or the coloured image produced by the unequal refrangibility of the different rays of colour which 
together produce white light. Owing to this difference of refrangibility a ray of white light, in passing 
through a single lens, such as the object glass of the above-mentioned telescope, is not refracted to the focus 
unaltered, but is decomposed or broken up into rays of various colours, and therefore tlie object when viewed 
with this instrument is so much coloured that distinctness of vision is impossible. Another great defect is 



96 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



spherical aberration, or indistinctness of the image produced by the spherical figure of the lens, which pre- 
vents call the rays from the object uniting at a common focus. This latter defect, however, Avas not of so much 
importance, inasmuch as it could be remedied by shaping the lens to a hyperbolic curve, or by making its 
two sides of different spherical curves. 

For years philosophers had been led astray by the statement of Newton that it was impossible to remedy 
the defect of chromatic aberration, and it was not till the year 1758 that the English optician, DoUond, 
discovered by experiment that such was not the case. On carefully examining various kinds of glass, he found 
that some specimens had a greater dispersive power, or produced when used as a telescope a greatly more 
coloured image than other specimens. This suggested to him that a perfect instrument might be made by 
combining lenses of different kinds of glass. In carrying out this idea he was entirely successful, for DoUond 

soon found that if a convex lens of the least dispersive power, or 
composed of crown glass, were united with a concave lens of great 
dispersive power or of flint glass, a telescope could be produced that 
would give an image almost free from colour {see (c) Fig. 25). 

This instrument received the name of the "Achromatic Tele- 
scope," or telescope that was free from colour. By this important 
invention of DoUond's the inconveniences of the old refracting 
telescope were done away with, for an instrument could now be 
made as powerful as the longest one hitherto employed, and only 
one-fifteenth of the length. Fortunately Dollond possessed a 
quantity of glass of superior quality, which enabled him at once 
to carry his invention to a high degree of perfection. The largest 
instruments he constructed were only about four inches in diameter, 
and this size was not surpassed for many years afterwards, owing to 
tlie difficulty experienced in securing flint glass of fine quality. It 
was not till the year 1830 that the manufacture of optical glass had 
been so far perfected as to enable opticians to construct achromatic 
telescopes with apertures of about nine inches. Several instruments 
of about this size were soon made for the observatories of Dorpat, 
Rome, and Munich, by the celebrated optician, Frauenhofer. As the 
manufacture of optical glass discs, for the construction of telescopic 
object-glasses, became more and more certain, opticians were 
encouraged to attempt the construction of larger instruments. 
In this they have been, within certain limits, entirely successful. 
Till the year 1860 achromatic telescopes had not been constructed larger than from twelve to fourteen 
inches in diameter. In 1862, however, one eighteen and a-half inches in diameter was completed for the 
Dearborn observatory, and this was soon followed by several others of slightly larger dimensions. In 1870 
even this large size of object-glass was surpassed by the magnificent instrument, with an aperture no less 
than twenty-five inches, that was made for Mr. Newall, of Gateshead. The American opticians, not to be left 
behind by the English, endeavoured to construct even a larger instrument, and in this they were so successful 
that in 1873 an object-glass twenty-six inches in diameter was produced for the Washington observatory, 
so superior in quality that it has justly been considered one of the finest specimens of the optician's art. 
From 1873 the size of the refracting telescope rapidly increased. In 1879 one twenty-seven inches in diameter 
was constructed for the observatory at Vienna ; and in the same year one twenty-nine inches, for the observatory 
of Paris. In 1880 one thirty inches was completed for the Nice observatory ; in 1882 another the same size 
for the observatory at Pulkowa; and in 1888 the largest instrument of this kind yet constructed — viz., the 




Fig. 26. THE LICK REFRACTOR. 



ASTRONOMICAL INSTRUMENTS. 



97 



great " Lick Refractor," with au aperture of no less than thirty-six inches [see Fig. 26). The difficulties 
to be overcome in the construction of this monster instrument were enormous. Numerous discs of 
glass had to be cast before suitable ones could be obtained, and it was only after about seven years of the 
most skilful labour possible in the present state of science and art that this optical masterpiece was 
successfully produced. 

THE REFLECTING TELESCOPE. 

Philosophers, realising the impossibility of overcoming the unequal refrangibility of the different coloured 
rays of light, gave up the idea of perfecting the refracting telescope, and directed their attention to the pro- 
duction of an instrument on some other principle. In 1639 Mersenne suggested the employment of a spheri- 
cally-shaped mirror, for forming an image which might, as in the case of the refracting telescope, be afterwards 
magnified by means of a small convex lens. The Scottish astronomer Gregory, of Aberdeen, proposed a similar 
arrangement in 1663, without having had any previous knowledge of Mersenne's suggestion. Gregory's 
instrument was somewhat different in principle from Mersenne's, for he substituted a parabolic reflector. 




Figs. 27, 28, 29. Different Kinds of Eeflecting Telescopes. 

The Reflecting Telescope : A, Large speculum ; B, Small concave mirror ; C, Convex mirror ; 
D, Small flat mirror ; E, Eye-piece ; F, Focus of large speculum. 



instead of the spherical one, for forming the image, and proposed the use of a small concave mirror placed 
outside the focus of the largo one, and situated in its axis. By this means the image of the distant object 
formed at the focus of the large mirror would be refie-cted backwards through a small hole in the great 
speculum to the eye-piece lenses, where it was conveniently magnified, as indicated in Fig. 27. Believing 
in the success of his instrument, Gregory went to London for the purpose of having one constructed, 
but this he failed to accomplish, as no workman could be found who could produce a speculum, and 
unfortunately the project had to be abandoned. 

About this time Newton had also turned his attention to the construction of reflecting telescopes, 
and having, in 1669, discovered a suitable alloy, he began to cast and grind a speculum with his own 
hands. Early in 1672 he completed two small instruments, one of which was about one iucli iu diameter, 
and had a magnifying power of thirty-eight (see Fig. 29a). The principle of Newton's telescope was 
somewhat different from that of Gregory's, as it had no small concave mirror, but a small perfectly flat 
one instead. This flat mirror was situated in the axis of the telescope, and inclined to it at an angle 
of 45 degrees, by which means the light rays were reflected through a hole in the side of the tube, and 
the image accordingly viewed at right angles to the axis of the instrument, as represented iu Fig. 29. 



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A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



The same year in which Newton completed his instrument, another form of reflector was proposed by 
Cassegrain. In arraogement, this instrument was similar to Gregory's, only, instead of a small concave 
speculum placed outside the focus, a small convex mirror situated inside the focus was suggested 
(see Fig. 29). In this latter form of instrument, the image, as in the refracting telescope, is inverted, 
while in Gregory's it is erect. Cassegrain does not seem to have actually constructed an instioiment of 
this kind, and it was not till the year 1674 that a reflecting telescope with a hole in the centre of 
the large speculum was produced. 

But little progress was made in the construction of reflecting telescopes for several years, owing to 
the difficulty experienced in obtaining a suitable alloy of metals for the mirrors. Accordingly, the first 
really powerful reflector was not made till 1718, when Hadley, the inventor of the sextant, constructed 
one, five feet long, on the Newtonian principle. This instrument was perfect enough to stand a magnifying 
power of 208 times, and revealed as much as an old refracting telescope of nearly 120 feet in length. From 
this time till the appearance of Herschel, reflecting telescopes were successfully constructed, but chiefly on the 
Gregorian principle. This form of 
telescope reached a high degree of 
excellence from the labours of 
Short, the Edinburgh optician. In 
1732, Short turned his attention 
to the construction of Gregorian 
reflectors, and in a very few years 
afterwards surpassed every one else 
in their production. One of his 
finest instruments was so beauti- 
fully finished, and so perfect in 
figure, that the King of Denmark 
offered for it a sum of 1200 




Fig. 29a. the first reflecting telescope, made by sir isaac newton. 



It is to Herschel, however, that 
we owe the general introduction of 
the reflecting telescope ; for, as yet, 

no discoveries had been made by this form of instrument, and it was only by Herschel's success that 
the reflector became universally noticed. As early as 1774 Herschel, having had his attention directed 
to the wonders of astronomy by the temporary employment of a small Gregorian reflector, began to construct 
instruments for his own use. He was so impressed with what was revealed to him by this instrument, 
that he desired to have a similar one for himself; but the cost being too great for his means, he 
attempted the construction of a telescope with his own hands. In this he was entirely successful; for, 
after great difficulty, he completed a Newtonian reflector of five feet in length. This v\^as soon followed 
by others, seven, ten, and even twenty feet long ; and during his lifetime it is said that he constructed 
no less than four hundred instruments, of various powers and sizes. The largest of all his instruments was 
completed, under the patronage of George III., in 1789. In the construction of this telescope Herschel 
surpassed all his former efi"orts, for it was actually forty feet in length, and four feet in diameter. No 
sooner was this giant specimen of the optician's art directed towards the heavens than it was discovered 
that Saturn had two more satellites, which, owing to their faintness, had hitherto escaped the scrutiny 
of astronomers. 

Herschel's telescopes were chiefly Newtonians, a form of instrument which is capable of being 
constructed with a high degree of perfection. One of the best specimens of this kind of reflector ever 



ASTRONOMICAL INSTRUMENTS. 99 



made was produced by Mr. Lassell, of Liverpool. It had a diameter of two feet, and wa.s so 
perfect in figure that he was enabled to discover by it the eighth satellite of Satuun and the single 
satellite of Neptune. This instrument was afterwards presented to the Observatory at Greenwich, where 
it is still used. 

The largest telescope, however, which has been constructed on this, or indeed on any principle, wa.s 
made by Lord Kosse. In 1840, this highly gifted nobleman completed a Newtonian reflector three feet 
in diameter, which, when employed in observation, was found to be an instrument of the highest excellence. 
But Lord Rosse was not satisfied with so large and splendid a telescope. Three years afterwards he 
gave to the world a still more striking proof of his great talent, and of the interest he had in the 
advancement of astronomical science, by successfully constructing a reflector six feet in diameter 
and fifty-six feet in length. This monster instrument is erected at Lord Rosse's estate at Parsonstown, 
in Ireland. It is suspended between two large walls, so that its movement is very limited, only 
amounting, in fact, to about eight degrees on either side of the meridian. Accordingly, a view of any 
celestial object can only be obtained when it is near its meridian passage, and only for about one hour 
at a time. 

The largest reflecting telescope yet constructed with a pierced mirror, was erected in 1870 at the 
Melbourne Observatory. It has a diameter of four feet, and is of the Cassegrainian principle. This 
instrument has been chiefly employed in observing and photographing the numerous nebulie and star 
clusters visible in the southern hemisphere. 

THE MODERN REFLECTOR. 

Till very recently it was usual to make the mirrors of reflecting telescopes of an alloy of copper 
and tin, a composition which is capable of receiving a high polish, and giving a brilliant reflection. But the 
specula thus produced were liable to tarnish through exposure to the weather, and could only be renewed 
by a process of polishing, an operation almost equivalent to the mirror's reproduction. This defect was in part 
remedied by Lord Rosse, who, from numerous experiments, greatly improved the composition of the alio}-, 
whereby its liability to tarnish under exposure was diminished. Foucault, however, entirely overcame the 
defect by his invention, which consists in making once for all a speculum of glass, and depositing upon 
it an exceedingly thin film of silver. By this means the reflecting telescope was perfected, for not onlj' 
was the great difficulty of the tarnishing successfully overcome, inasmuch as the film could be renewed 
as often as required without injuring the figure or delicate curve of the mirror, but a far more accurate 
curve could be given to glass than to a speculum formed of metal. Still further, the " silver-on-glass " 
reflector not only gives a more accurate image than the metal speculum, it also reflects more light. 
Though the silver film is only about the one-hundred-thousandth of an inch in thickness, it is nearly 
opaque, and at the same time so brilliant that it reflects ninety out of every hundred rays of light which 
fall on it. Accordingly, a modern reflecting telescope of about fourteen inches in aperture is a more 
powerful and perfect instrument than one of Herschel's eighteen inches in diameter. For several years 
the Author has employed one of these glass reflectors at his observatory with great advantage. It has 
an aperture of over thirteen inches, and a length of eleven feet; and is so perfect in construction that by 
its aid the finest views of the various celestial objects have been obtained. 

APPLICATION OF THE TELESCOPE. 

It was not till the year 1G40 that the telescope was employed for sighting astronomical measuring 
instruments. Previous to that time the " optic tube " had been used only for viemng purposes, as it 
never occurred to astronomers that an angular instrument could be more accurately pointed to a celestial 
object by aid of telescopic sights than by the unaided eye. The young English astronomer, Gascoigne, 



100 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



seems to have been the first to have employed this method, by placing in the focus of the object-glass 
fine cross hairs. But Gascoigne went further : he not only employed telescopic sights, he also used the 
instrument for determining very minute angular distances. This he accomplished by placing in the 
focus of the telescope a graduated scale, or micrometer as it is now termed, by means of which the 
angular diameter of any celestial object could be measured, or the distance between close objects accurately 
determined. 

Though Gascoigne seems to have been the first to have employed the micrometer, it is really to 
the Continental astronomers of about the middle of the seventeenth century that science is indebted 
for the application of the instrument to the telescope. Huygens proposed the use of an angular slip 
of metal situated in the focus of the object-glass, in such a manner that it could be pushed gradually 
inwards until the particular object was exactly eclipsed, from which its apparent diameter could be 
found. The Marquis of Malvasia invented a different form of micrometer, consisting of a reticule, or 
fine network of silver threads, the distance between which could be accurately determined by observing 
the intervals occupied by a star or planet in passing between them in its apparent diurnal movement. 
The most valuable invention of this kind, however, was due to the independent suggestions of Auzot 
and Hooke. These astronomers pointed out that the reticule micrometer would be of considerably more 
value for delicate measurement if one of the threads had a parallel movement, by means of a fine screw. 
Accordingly, this form of micrometer, which is the one now principally employed, consists of two sliding 
metal frames, across which two exceedingly fine wires are stretched {Fig. 30). By means of an accurately 
made screw the frames which carry the wires are made moveable, and therefore the wires can be placed 

at any required distance from each other. As the distance 
between the threads of the screw is accurately known, the 
number of revolutions, and part of a revolution, which the 
screw has made in movmg the frame from the point where 
the two wires were exactly behind each other, to tbe position 
where they embraced the diameter of the object to be measured, 
is all that is required to be known in order to determine the 
angular distance. To simplify the numbering of the revolutions, 
a scale is inserted parallel to the screw, by which means the 
exact number of revolutions which the screw has passed over can be ascertained by observation, while 
the exact portion of a revolution can likewise be found, from the large graduated head of the screw. 
Thus, for example, the apparent diameter of a planet can be determined by first bringing the two wires, 
B, C, together by the screw movement, and then turning the screw until the wires are made to embrace 
the planet's disc, when, by means of the scale and graduated head, the number of revolutions, and part 
of a revolution, can be easily found, and from these the angular diameter of the planet.' When this 
instrument is constructed with great refinement, it is capable, when applied to a large telescope, of 
measuring very minute angles, not unfrequently to the fraction of a second of arc. 




Fig. 30. the parallel wire micrometer. 
A, Horizontal wire; B, C, Movable vertical wires. 



THE TRANSIT INSTRUMENT. 

This most valuable instrument of modern astronomy, by means of which the positions of the various 
heavenly bodies have been so accurately determined, was invented in 1644 by the Danish astronomer, 
Roemer. Previous to that time the positions of the- different celestial objects had, for the most part, 
been determined by observations when out of the meridian. Tycho had indeed seen the great advantage 
of meridional observations over those made when the object was in other parts of the sky, but the 
method he adopted did not give much more accurate results than those already employed. His arrangement 
consisted of a large mural quadrant, whose plane was made to coincide as nearly as possible with the 



ASTRONOMICAL INSTRUMENTS. 



101 




meridian. By means of a hole in the wall, near the apex of the instrument, in which a sight was placed, 
and a corresponding sight on the graduated limb of the quadrant, the instant of a celestial object's 
passage across the meridian was determined ; while the position of the lower sight on the limb gave 
the exact altitude, from which its equatorial distance or declination could be found. It was by such 
means that Tycho sometimes determined the right ascension and declination of the different heavenly 
bodies, or those important celestial co-ordinates which are employed by astronomers for indicating the 
positions of objects on the star-sphere. After the telescope had been 
some time in use, astronomers, carrying out Roemer's suggestion, 
were enabled to determine these positions with greater accuracy by 
means of a much smaller and less cumbersome apparatus — viz., the 
transit instrument. 

This instrument, as one might suppose, received its name from 
being designed to observe the transit of celestial objects across the 
meridian. Accordingly, it consists of a telescope mounted on trunnions 
like a cannon, so as to have but one movement — viz., in a vertical 
plane. This direction of movement is, by accurate adjustment, made 
to coincide with the meridian, and, consequently, the horizontal axis on 
which the instrument swings lies exactly east and west. The extremities 
of the axis, or the pivots as they are called, rest on " Y " bearings, 
which are securely fixed on the top of two massive stone piers or 
pillars (see Fig. 31). These pivots require to be formed of some hard 
material and must be of the most accurate construction, for not only is 
it absolutely necessary that they should be of exactly the same size, 
but also continuations of the same geometric cylinder. When this is 
the case, and the instrument accurately adjusted to the meridian, the 
centre of the field of view, or the optical axis of the instrument, will, when the telescope is turned 
completely round, trace out accurately the meridional great circle. 

By this means the exact instant of an object's transit over the meridian can be found. To insure 
the greatest possible accuracy, the field of view is divided into spaces by seven exceedingly fine \vires, 
or, very often, lines formed by threads of spider web (see Fig. 32). The time of the object's passage 
across each of the wires is very carefully observed, and the average of these times 
gives more accurately than a single observation the instant of meridian transit. In 
order to set the instrument to the altitude of the object to be observed, a small 
graduated circle is attached, the index of which, when adjusted, enables the observer 
to place the telescope at the required angle for the object's passage through the field 
of view. 

Until very recently the instants of tranait were determined by " eye and ear ' 
observation, the eye discerning the instant of the object's bisection by the wire, and 
the ear counting the beats, or seconds of the astronomical clock. Now, however, this 
is accomplished more simply and accurately by the use of an instrument called " the 
chronograph." This instrument consists of a revolving drum, driven by clockwork, 
on which there is placed a sheet of paper. As this cylinder revolves, a small electro- magnetic pen is 
made to move gradually along, and at the same time caused to record notches on the paper at regular 
spaces, or at perfectly regular intervals of time. This is accomplished by an electrical arrangement 
connected with the observatory clock. With each beat of the pendulum the circuit of the battery is 
closed and broken again. The closing of the circuit gives a small lateral iiKn-omcnt to the registering 



Fig. 31. the transit ixstrument. 
C, Large graduated Circles. 
E, Micrometer Eye-piece. 
L, Level. 

M, Microscopes for reading Divisions 
on Circles. 




Fig. 3-2. the field 
OF view op the 
transit instru- 
ment. 



102 A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



pen, so that the seconds of the standard clock are accurately recorded on the sheet of revolving paper. By 
means of a second pen connected with a key, which the observer holds in his hand, an intermediate notch 
can, at any time, be made. Whenever a star, or other celestial object, is exactly bisected with one of the 
wires, the observer has only to touch the key in order to cause the pen to make a mark on the paper, 
and permanently record the instant of transit ; for, by observation of the position of the notch thus made, 
not only is the exact second determined, but, by subdivision, the smallest fraction of a second as well. 

The transit instrument is accordingly employed for determining the instant of meridian passage, which it 
is capable of doing with the greatest accuracy, and from this the right ascension, or distance of an object from 
the vernal equinoctial point. It can only, however, determine the altitude very approximately, as the circle 
attached to it is too small for accurate measurement of arcs on the meridian. Until recently these arcs were 
measured by means of a large circle of from six to eight feet in diameter, firmly attached to a massive stone wall 
built in the plane of the meridian. By means of several microscopes, and minute divisions on the limb, the 
altitude, and from this the declination, could be fixed with great accuracy. Accordingly, by the employment 
of these two instruments — viz., the transit instrument and the mural circle, astronomers are enabled to 
minutely determine the celestial co-ordinates. 

The use of these instruments, however, requires separate observations, and, therefore, different observers. 
To overcome this disadvantage, and to simplify the observations as much as possible, an instrument has been 
designed to enable a single observer to determine simultaneously the right ascension and declination. This 
instrument, as might be supposed, is simply a combination of the two above-mentioned — viz., the mural 
circle and the transit instrument, and is called the meridian, or transit circle. It consists essentially 
of a transit telescope proper, with large graduated circles attached to its axis in such a manner as to 
revolve with the telescope. Its construction requires the greatest mechanical skill, guided by the highest 
scientific knowledge. All the parts must be made with the greatest care, and in such a manner as to insure 
perfect rigidity, and freeness from the slightest vibration and flexure, defects which would vitiate the observa- 
tions. Usually the circles of this type of instrument have a diameter of from two to four feet, as it is found 
that if constructed of larger size, less accuracy is actually attained, owing to the greatly increased strain and 
flexure produced by the cousequent increase of weight. In dividing these circles as precisely as possible, 
and in providing the greatest accuracy in reading the graduations, the utmost resources of mechanical art are 
employed. As, however, it is absolutely impossible in the construction of any instrument to reach perfection, 
minute errors are accordingly produced, which it is the duty of the astronomer to discover, and allow for, in 
his observations. By means of this instrument the declination, or north polar distance, of an object can be 
determined to within less than one second of arc, an angle which is so minute that, even on a circle of about 
four feet in diameter, it only amounts to the one-ten-thousandth of an inch, which shows the necessity for 
the finest workmanship. 

THE OBSERVATORY CLOCK. 

The necessary adjunct to the above-mentioned instruments is the sidereal clock, for, without accurate 
time, the instant of meridian passage would be unknown, and the right ascension could not be easily 
determined. It is only within the last two hundred years that reliable time-keepers have been obtainable, 
as previous to the year 1657, no certain method for controlling a clock movement was known. Though 
Galileo had already discovered the law of the pendulum, it was Huygens who first applied that gravitational 
governor to the construction of clocks — an application which has done as much to advance astronomical 
science as the invention of the telescope. 

In construction the astronomical clock differs from that of any other, only in its parts being more carefully 
produced. As a matter of convenience it is made so as to beat exact seconds of time. This depends entirely 
on the length of the pendulum, whose slowness of movement increases with its length. The proper length 
that a pendulum ought to have in order to beat true seconds, was first determined by Huygens, who fouod that 



ASTRONOMICAL INSTRUMENTS. 



103 



approximately it amounts to about 39 inches. It is slightly different, however, for diflferent latitudes, increas- 
ing in length as the place approaches the poles. As the exact indication of time entirely depends on the 
regularity of the pendulum's vibrations, it is necessary that it should be invariable in length. This it is 
difficult to preserve, as no single substance has ever yet been found of which a pendulum can be constructed 
which is not liable to contract and expand under changes of temperature. 

To overcome this defect, the compensated pendulum has been invented — a pendulum which under any 
change of temperature retains its adjusted length. The one most commonly used is known as Graham's 
mercurial pendulum, after its inventor. It consists of a long steel rod, suspended by a spring, at the foot of 
which is a glass jar three or four inches in diameter filled with mercury {A, Fig. 33). By this means the centre 
of gravity of the mass of mercury always remains at the same distance from the centre of suspension. Under 
an increase of temperature, for example, the steel rod lengthens, but as the mercury also expands, it rises in 
height, and just the required amount to keep the centre of gravity at the same distance from the centre 
of suspension. Another form of composition pendulum is a modification of the old " gridiron " one invented by 
Harrison. As indicated in the figure B, this pendulum is composed of a zinc tube and steel 
rods. These are arranged with the rods outside the tube, and supporting it at the bottom ; 
while an internal steel rod, which carries the heavy leaden bob, is suspended from the top of 
the tube. While the steel rods lengthen from a rise of temperature, the zinc tube also 
increases its length, but in an upward direction, and, therefore, the lead cylinder is raised by 
the tube exactly the amount it was lowered by the expansion of the rods, or under changes 
of temperature the length of the pendulum remains invariable. 

The next important part of the astronomical clock is the escapement, or wheel, which is 
under the immediate control of the pendulum. The one generally used is known as Graham's 
" dead-beat" escapement, from the second hand beating the seconds without any recoil. 
With each swing, the pendulum allows the escape wheel to advance one tooth, and thus indi- 
cates on the. dial one second of time. For convenience of reading the time, the second hand of 
astronomical clocks is very conspicuous, while the hour-hand makes but one revolution per day, 
instead of two as in ordinary clocks, the hours being numbered continuously to twenty-four. 

The clocks used in observatories are of two kinds — viz.,the mean time clock and the sidereal 
clock. The former of course indicates the true mean solar time, and consequently makes a 
complete revolution once every twenty-four hours ; while the latter has no direct connection 
with solar time, as it completes a revolution in twenty-three hours fifty-six minutes, or in the 
time occupied by the earth in making a complete rotation. Thus the sidereal clock keeps 
pace with the apparent movement of the star-sphere, and therefore indicates the position of the 
stars in the sky. It is so adjusted that it indicates Oh. Om. Os. when the vernal equinox, or 
the first point of Aries, is on the meridian, and accordingly shows at any time the hour of 
right ascension that is passing the meridian, or indicates, as it is called, the sidereal time. When accurately 
regulated, on the other hand, it is employed, in conjunction with the transit instrument, in determining 
the right ascension of objects, for the exact instant of time indicated by the clock when the object is bisected 
by the central wire in the focus of the telescope is its tme right ascension, or distance in time from the first 
point of Aries. 

THE EQUATORIAL. 
This is the name given to a certain style of mounting for the telescope when principall}- employed for 
viewing purposes, as by means of it the instrument can be made to sweep out curves on the celestial sphere 
parallel to the equator. Accordingly, the principal axis round which the telescope swings is not upright, or 
vertical as in the case of small instruments, but inclined to the horizontal at an angle equal to the latitude of 
the place, and directed to the pole of the heavens. The chief axis, or the polar axis as it is called, is thus 




Fig. 33. the 
compensated 
pendulum. 

s,Suspensio n 
Spring ; 

C, Jar of Mer- 
cury y 

L, Cylinder of 
Lead. 



104 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 




Fig. 34. the equatorial telescope. 



placed exactly parallel to the axis of the earth, and, therefore, by one movement, the instrument can follow the 
apparent course of an object produced by the rotation of our globe. Passing through the polar axis, and lying 
at right angles to it is another one called the declination axis, to which the telescope is fixed. By means of 

this axis the telescope can be pointed to any particular part of the celestial 
sphere, or to any required declination. This is conveniently accomplished 
by aid of a graduated circle attached to the opposite end of the arm which 
carries the declination axis. At the foot of the polar axis there is a similar 
circle, called the hour, or right ascension circle, by means of which the 
telescope can be pointed to any hour angle, or distance in time east or 
west of the meridian. Thus, by aid of these two circles, the telescope 
can be directed to any part of the heavens, or pointed during the day or 
night to any invisible object. If, on the other hand, an object be 
discovered, its position in the heavens, or its right ascension and declina- 
tion, can at once be determined by reading the declination and right 
ascension circles. 

The equatorial mounting can be divided into two kinds — viz., the 
English and German. In the former the telescope swings between two 
long pillars which terminate in two pivots. These are supported at top and 
bottom, and accordingly form the polar axis of the instrument. This form 
of mounting is adopted at Greenwich Observatory for the large refracting 
telescope. The Author has successfully employed this style for his reflector of over thirteen inches aperture, 
as indicated in Fig. 3i.* In this case the polar axis is about fourteen feet in length, and is so rigidly 

constructed that great steadiness and accuracy of movement 
is obtained, from which the Author has been enabled to 
produce several very fine celestial photographs (see Frontis- 
piece). 

One of the disadvantages of the English equatorial is 
the impossibility of obtaining by it a view of any object 
near the pole. This is entirely overcome in the German 
mounting, which is now almost universally employed for 
the refracting telescope. In this form the polar axis is com- 
paratively short, and the telescope, instead of swinging cen- 
trally, as in the case of the English form, is supported on 
one end of the declination axis, its weight, which is generally 
considerable, being counterpoised by a system of heavy 
weights, sliding on levers at the other end of the declina- 
tion arm. Figure 35 is a representation of this style of 
mounting applied to a large refractor (see also Fig. 26) ; 
while Fig. 36 is a representation of the German equatorial 
mounting applied to a glass reflecting telescope twelve 
inches in diameter, constructed by the Author. 

The great advantage of the equatorial mounting for 
large instruments, over any other, is derived from its con- 
venience for following celestial objects with only one motion. If the principal axis were vertical, as in the 

* The instrument of which Fig. 34 is a view, was presented to the City of Edinburgh Observatory by Robert Cox, Esq., 
M.A,, F.R.S.E. 




Fig. 35. a modern refracting telescope 
equatorially mounted. 



ASTRONOMICAL INSTRUMENTS. 



105 



altitude and azimuth stand employed for small telescopes, the instrument would require to be raised, when 
following an object in the eastern portion of the sky, and continually lowered, when viewing in the west. 
The equatorial, however, as already mentioned, from the inclination of the polar axis, is enabled to trace out 
curves on the star-sphere exactly the same as those described by the apparent movement of celestial objects. 
As this motion is produced by the rotation of our globe it is perfectly uniform, and consequently cbckwork 
can be applied to drive the polar axis at the same rate 
as the earth. By this means celestial objects can be 
viewed for hours at a time without passing out of the 
field of view, as by the clock movement the telescope is 
made accurately to keep pace with the motion of the 
object. Celestial photographs can also, by aid of the 
driving clock, be obtained, for, notwithstanding the 
apparent motion of the heavenly bodies, the movement 
of the telescope can be so accurately regulated, that even 
the smallest stars can be imprinted on the photographic 
plate with perfectly round discs, which they could not 
have if the instrument had the slightest irregular move- 
ment. 

THE SPECTROSCOPE. 
This is certainly the most wonderful instrument 
employed by the astronomer, though only of comparatively 
recent invention. Although the decomposition of light, pro- 
duced by being passed through a prism or wedge-shaped 
piece of glass, was discovered by Kepler and Newton, it was 
not till 1814 that the spectroscope was first used. Pre- 
vious to that year, WoUaston, while casually looking 
through a prism at a narrow opening in a window, 
observed that the coloured band, or spectrum, was crossed 
by a number of dark lines parallel to the slit. This led 
to the invention of the spectroscope, and to the mapping 
of the lines by the German optician, Fraunhofer (see Plate 
19.) The essential part of this instrument consists of a 
triangular prism, by means of which the light is dispersed 
or broken up into a coloured band. But the light in passing through 




Fig. 36. a modern reflector equatori.\lly mounted, 
constructed by the author. 



prism is not only decomposed, it is 
also refracted out of its original course, the amount of divergence depending on the colour. The nearer the 
ray approaches the red colour, the less it is refracted, and thus the red or yellow rays in a beam of white light 
are not bent so much out of their course as the blue or violet rays. 
The image of the slit of the spectroscope, when viewed through a 
prism, is, therefore, of a considerable breadth, and contains all the 
colours of the rainbow. 

In its simplest form the spectroscope contains only one 
prism, which is placed between two telescopic tubes (Fig. 37). 
At the outside end of one tube there is placed the slit S, a very 
narrow opening, which, by a delicate screw movement, can be 

accurately adjusted to the required breadth. At the other end of the same tube, or next the prism, a small 
achromatic lens is situated, for the purpose of causing the divergmg rays from the sUt to pass through 




Fui. 37. M.Ml'LE ^I'tCTROsCOl'l . 



106 



A FOFULAB HANDBOOK AND ATLAS OF ASTRONOMY. 



the prism parallel to eacli other. After passing through the prism, and being refracted by it towards 
its base, the rays now fall on the object-glass of the small viewing telescope, by which means they are 
bent to a focus, Avhere the spectrum is formed, and where it can conveniently be magnified by the eye-piece lens. 
When applied to the telescope, and especially when used in examining the light of the sun, a considerable* 
number of prisms are often employed in order to secure as great a dispersion as possible. Sometimes, too, 
instead of a battery of prisms, a " diffraction grating," or flat piece of speculum metal ruled with numerous 
fine lines, so close together that there are at least 15,000 in a single inch, is used, especially when the produc- 
tion of a very highly magnified solar spectrum is desired. Figure 38 is a representation of a double prism 
astronomical spectroscope in the possession of the Author. This type of instrument is chiefly employed in 
the examination of the spectra of stars ; and, when so used, a cylindrical convex lens conveniently takes the 
place of the slit. For the solar spectrum, however, and for the spectra of planets and nebulae, the slit cannot 
be dispensed with. In the Author's instrument the slit can be very accurately adjusted by means of a tine 
screw with graduated head, which records an opening as small as the thousandth of an inch ; while, for the 
purpose of measuring the distances between the lines of the spectrum, a delicate micrometer, in the 
focus of the viewing telescope, registers as minute a distance as the ten-thousandth part of an inch. 

As already mentioned, WoUaston, at the beginning of the present century, accidentally discovered 
that the solar spectrum contained numerous dark lines, and Fraunhofer with great care determined the 
positions they occupied. These lines were soon found undoubtedly to belong to the sun, as when the slit 
of the instrument was directed towards some artificial light, only a coloured band, or continuous spectrum 
was observed. It was not, however, for many years after their discovery, that their existence could be 

accounted for. Now it is known with certainty how they are produced. 
Each incandescent body, whether solid, liquid, or gaseous under a high 
pressure, gives a continuous spectrum, without lines ; while, if it is sur- 
rounded with vapours, these will absorb certain parts of the spectrum, 
and produce dark lines. These lines would appear luminous if the 
vapours surrounding the incandescent mass were glowing with heat, and 
the overpowering brilliancy of the incandescent body removed. This is 
proved to be the case by what is known as the reversal of the spectrum. 
When, for example, the metal sodium is burnt in the colourless 
Bunsen flame, two bright lines are seen in the yellow part of the 
spectrum {see " D" line, Plate 19). If, on the other hand, a brilliant 
light be placed behind the sodium vapour, two dark lines will be seen 
instead, and these will be found occupying exactly the same position in 
the spectrum as the bright lines. Appljdng this experiment to the sun, 
the bright sodium lines can, by means of a small reflecting prism placed in front of the slit of the 
spectroscope, be seen in the field of view alongside of the solar spectrum. When thus examined it is 
found that they coincide exactly with two dark lines in the spectrum of the sun, which proves that these 
latter owe their existence to sodium vapour surrounding the solar globe. 

In the same manner hundreds of other lines have been identified, and accordingly the composition of the 
solar atmosphere revealed. The following elements are known with certainty to compose a large portion of 
the vapours surrounding the sun : — 




Fig. 38. 

THE author's spectroscope. 

C, Cylindrical Lens. 
S, Slit. 
FP, Frisms. 
T, Viewing Telescope. 



Barium. 
Calcium. 
Chromium. 
Cobalt. 



Hydrogen. 
Iron. 

Magnesium. 
Manganese. 



Nickel. 
Platinum. 
Sodium. 
Titanium. 



while there is the strongest evidence for supposing that the following also exist in the solar atmosphere : — 



Plate 19. 




Cof.slrult»d by W PecK Ed.nb 



ASTRONOMICAL INSTRUMENTS. 



107 



Aluminium. 

Cadmium. 

Carbon. 



Copper. 
Lead. 

Molybdenum. 
Oxygen. 



Palladium. 

Uranium. 

Vanadium. 



Like the solar spectrum, the spectra of the stars are also crossed with several dark lines, which proves 
that these orbs are indeed suns, or, like the great centre of our system, incandescent gaseous masses 
surrounded with glowing vapours. But not only does the existence of the lines in the stellar spectra prove that 
these orbs are suns, and that they are composed of many well-known terrestrial materials, the difference of 
the grouping of the lines also reveals, as mentioned in Chapter III., the fact that the stars are arranged 
into different groups. 

The nebulae, on the contrary, give no dark lines at all, not even a continuous spectrum, but instead a 
spectrum composed only of bright lines. This shows that they are in a condition vastly different from that 
of the stars, that instead of being incandescent gaseous masses under great pressure, they are simply uncon- 
densed masses of luminous vapour. 

Not only, however, is the spectroscope employed in the analysis of the various heavenly bodies, it is also 
used with success for determining the velocity at Avhich they are moving. This 
it is capable of doing irrespective of the object's distance ; as its motion affects 
the velocity of the light rays travelling from it towards us. If, for instance, a 
star be journeying away from our -system, the light waves will be lengthened, and 
if travelling towards us, they will be shortened by the actual velocity of the star's 
motion in the line of sight. Accordingly, the lines of the stellar spectra do not 
exactly coincide with those formed by the burning of terrestrial substances, but are 
slightly displaced, to the one side or other, of the corresponding terrestrial spectral 
lines. As difference of colour is simply a difference of length in the weaves of 
light, the violet being the shortest, and the crimson the longest, the direction of 
displacement gives the direction of the star's motion, and the amount of displace- 
ment the actual speed of the star in the line of vision. If, for example, the lines 
are displaced towards the blue end of the spectrum, then the motion of the star 
is being added to the velocity of light, which shows that the star is moving towards 
us. On the other hand, if the displacement happens to be directed away from the 
blue end, or towards the red part, the waves have been lengthened by the star's velocity in travelling away 
from our system. By this means the speed at which the stars are journeying in the line of vision, either from 
or towards us, can be determmed with approximate accuracy ; for the amount of displacement of the lines 
measured in the field of the spectroscope, gives the rate at which the star is moving in proportion to the velocity 
of the wave lengths of light ; and from this the actual velocity of the star in its orbit can be found (see page 18). 




Fig. 39. 

altitude axd azimuth 

instrument. 



OTHER ASTRONOMICAL INSTRUMENTS. 

Besides the instruments already mentioned for determining the positions of objects, there is the Altitude 
and Azimuth instrument. As its name implies, this instrument is constructed for the purpose of determining 
horizontal and vertical angles. This it is capable of doing with great accuracy, by means of two finely 
graduated circles situated at right angles to each other. Figure 39 is a vie^V of one of these instruments used 
by the Author. By aid of the delicate levels attached to the circles, the instrument can be accurately adjusted, 
and valuable observations made of positions of celestial objects when situated at any part of the heavens. 

Another very important instrument employed in obser\atories is the Prime Vertical Transit. This, like 
the ordinary transit instrument, seems to have been invented by Roemer. It is simply a transit instrument, 



108 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



but, instead of swinging in the meridian, is adjusted to the east and west line, or to the prime vertical. Roemer 
did not use this instrument much, and it was not employed by astronomers till Bessel pointed out its great 
value for accurately finding the latitude by means of time observations of stars crossing the prime vertical, near 
the zenith, and also for determining the declinations of stars. 

Among the portable instruments that the astronomer sometimes employs, the most important is the 
sextant. Though Hooke, as early as the beginning of the eighteenth century, had suggested the use of a 
reflecting instrument for measuring angles, and though Newton was doubtless the first who actually constructed 
such an instrument, or one resembling the modern sextant, it is to Hadley that science is indebted for its 
employment. Without knowledge of its previous invention, this invaluable instrument was re-invented almost 
simultaneously and independently by Hadley, in England, and Godfrey, in America, in the year 1730. 

Unlike other astronomical instruments, the sextant can be employed at sea, as observations made by it 
are not in the slightest affected by the motion of the ship, which renders it of the greatest service to the 
mariner, enabling him, in conjunction with the chronometer, to determine his position at sea with surprising 
accuracy. As represented in Figure 40, the modern sextant consists of a light metal framework, with suitable 
handle at back. This frame carries the graduated limb of the instrument, and the small mirrors for reflecting 

the images of the celestial object and the distant horizon. The limb only 
contains part of a circle, and is usually graduated to 120 degrees. On 
the limb, and moving round the centre of its arc, is the index arm with 
index mirror at top, or immediately over the pivot of the instrument. 
On the left-hand side is a stationary mirror, the top half of which is 
unsilvered. This is called the horizon-glass, because it is through this 
that the horizon is viewed. When employed in measuring altitudes, the 
instrument is held vertically, and turned so that the horizon is seen by 
the small telescope through the transparent part of the horizon-glass. 
The index arm is then moved outwards, or towards the horizon-glass, 
until the index mirror, which moves with it, reflects the celestial object 
from the silvered portion of the horizon-glass into the field of view of 
the small telescope. The object and the horizon can thus be made 
apparently to touch, and the angle, degrees, minutes, and seconds, 
which the arm has moved over in bringing the index-glass into this 
position, as indicated on the graduated limb, is the angular height of the object above the horizon. 

There are several other instruments employed by astronomers for special work, and therefore of special 
design, but they are not of so great importance as those already mentioned. Among these may be mentioned 
the zenith telescope, the heliometer, the photometer, or instrument for measuring the quantity of light 
emitted by the various stars ; the siderostat, heat measuring appliances, and celestial photographic 
apparatus. 

SUITABLE INSTRUMENT FOR A PRACTICAL STUDY OF THE HEAVENS. 

Having described the more important instruments employed by astronomers, it only remains to 
mention one that could be advantageously used by the reader in a practical study of the different 
heavenly bodies. The smallest size suitable for this purpose is either a refracting telescope of about 
three inches aperture, or a silvered glass reflector with a diameter of about four inches. By means of 
such an instrument, which may conveniently be used at an open window, striking views can be obtained 
of the more interesting celestial objects, as it would reveal the spots in the sun, the mountains of the 
moon, the phases of MERCURY and Venus, the belts of Jupiter, the ring of Saturn, and many double 
stars. Such an instrument, if of good quality, will bear a magnifying power of from two to three 




Fig. 40. the sextant. 
T, Telescope. I, Index Glass. 

S, Horizon Glass. D, Dark Glasses. 



hundred times, depending on the kind of object examined, 



ASTRONOMICAL INSTRUMENTS. 109 



The magnifying power of any telescope depends entirely on the proportion between the focal lengths 
of the object-glass and eye-piece lens. If, for example, the object-glass has a focal length of forty inches, 
and the eye-piece one inch, then the magnifying power would be forty. If the eye-piece, on the other 
hand, were only half-an-inch in focus, then the power would be double this, or eighty diameters. 
Accordingly, the greater the proportion between the focal lengths of the eye-lens and object-glass, the 
higher the magnifying power. 

This, however, cannot be increased indefinitely, as each instrument has a limit beyond which 
additional magnifying power cannot be applied. In the first instance, the power is regulated by the 
size of the object-glass, as an increase of power without increase of aperture gi-eatly diminishes the 
brilliancy of the object. When brightest, the magnifying power is the lowest possible that can be 
applied, and this lowest magnifying power also depends on the diameter of the object-lens. If less than a cer- 
tain proportion to the aperture, the diminished image of the object-glass in the eye-piece would be larger than 
the pupil of the eye, and, consequently, all the light from the object-glass would not enter the eye at one 
time. As the diameter of the pupil of the eye amounts, on the average, to about one-fifth of an 
inch, a sufficient magnifying power has to be applied to diminish the image of the object-lens to 
this size. The lowest magnifying power that will do this is easily determined for any size of telescope, 
by multiplying the diameter of the object-glass by five ; so that in a three-inch instrument the lowest 
magnifying power will be fifteen times. 

When the magnifying power, as above mentioned, is the lowest possible, the instrument has then 
the greatest space-penetrating power of which it is capable. Accordingly, this power depends entirely 
on the aperture of the telescope, irrespective of the focal length ; while the magnifying power, though 
certainly limited by the diameter of the object-glass, yet depends in a manner on the focus. But 
there is still another power that a telescope may be said to have — one which depends neither on 
the aperture nor on the length of focus, but on the quality of the object-glass itself. This, of course, 
depends on the nature of the glass and the fineness of its polish, and also on the accuracy of its 
curved surfaces. If these details are not attended to in the construction of the instrument, it will 
not be at all suitable for astronomical purposes, though it may give fairly good views with low powers 
of distant terrestrial objects. 

It is, therefore, necessary to test the instrument for any defects that it may have. For this purpose 
a sheet of printed figures in the daytime, and double stars at night, are the most suitable. If not 
truly corrected for chromatic aberration, the edges of the figures on the sheet of paper in the daytime 
will appear coloured; while if spherical aberration exists, it will be revealed in the general mistiness of 
the image when at its sharpest focus. During the night the same defects will be at once perceptible 
when the instrument is directed to the moon, planets, or stars. The Moon, Vekus, and Jupiter are 
the severest test-objects for achromatism ; while double stars easily reveal the more serious defect of 
spherical aberration. The Pole Star is a particularly good object for the test of defining power, as the 
faint companion can only be seen in the finest instruments. The following double stars should also be 
easily seen by aid of a three-inch aperture, with a power of about eighty diameters. 



a, PiSCIUM. 

Polaris, 

X, Arietis. 



a, Geminordm. 
X, Leonis. 
f, Herculis. 



II, Draconis. 

^, Urs.e ^Iajoris. 



Another very good test for instrumental defects is a star of the second magnitude, as any imperfection is 
revealed by the star's disc being surrounded with numerous rays. If these are equally distributed round the 
central disc, the fault belongs to the object-glass, and cannot be remedied ; but if seen only on one side, then 
the large lens is not truly adjusted, and may be made so by unscrewing the cell in which it is contained. 



no 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 




Though it may not at first seem so, a suitable stand is of the greatest importance, for it not unfrequently 
happens that by means of a defective stand, a good instrument is rendered nearly useless. Stability of 
structure is the first consideration that should be given in the choice of an instrument ; as it is of vastly more 
importance than appearance. Without steadiness it is impossible to obtain good views, even with a perfect 
object-glass ; while without vibration an indifferent instrument may be employed with advantage. With a 
telescope less than one inch in diameter, the French astronomer Lacialle determined the positions of no less 
than nearly 10,000 southern stars, but his instrument was firmly mounted. 

The simplest form of stand suitable for a telescope about the same size as that above described, is what 
is known as the " pillar-and-claw " stand (Fig. 41). By means of this stand two motions can be imparted to 

the telescope, one in a vertical direction, or in altitude ; the other horizontally, or 
in azimuth. The pivots on which these two movements are made, ought to be 
sufficiently close so as to retain the telescope in any position, and at the same 
time smooth enough to enable the instrument to be moved without jerking. In 
the more expensive stands of this form, several sliding rods, fitted with a rack- 
work, are attached to the base of the pillar, by means of which the instrument can 
be easily moved in altitude. Sometimes, too, a screw movemejit is provided in 
azimuth, which adds greatly to the ease of management of the telescope. This 
type of stand can be conveniently used at an open window, by being placed on a 
small table. If, however, access be obtained to a garden, a taller stand is necessary. 
For this purpose a light tripod, or garden stand, is often provided, by means of 
which the telescope can be more advantageously employed in the open air. If 
such a tripod be placed so that one of the legs points as nearly as possible 
towards the elevated Pole of the heavens (i.e., the North Pole in the Northern, 
and the South Pole in the Southern Hemisphere), then by gradually pulling out 
that leg till the vertical axis of the telescope points approximately to that Pole, a serviceable makeshift for an 
equatorially-mounted instrument will be obtained, by means of which stars can be much more readily 
followed, than if the axis of the instrument be kept upright. 

One of the most important additions to such an instrument is a Finder, or a very small telescope fixed on 
the tube of the large one, in such a manner that its axis lies parallel with that of the large instrument. 
In the focus of the object-glass of the finder, two wires are placed crossing each other at right angles. 

By means of adjusting screws, their crossing-point can be made to coincide 
with the centre of the field of view of the large telescope. The finder having 
but a very low magnifying power, it accordingly takes in a considerable 
part of the heavens, and therefore the object to be viewed can be found in 
its field without difficulty; and when once obtained is, by moving the 
telescope, simply brought to the centre of the cross hairs, when it will be 
seen in the field of view of the large instrument. 

Generally, small astronomical telescopes are supplied with several 
eye-pieces, which are of two kinds, negative and positive. The former is often called the achromatic, or 
Huyghenian ; the latter, the Ramsden, or positive eye-piece. The Huyghenian consists of two plano-convex 
lenses, placed at a distance from each other equal to one-half the sum of their focal lengths, and with their flat 
sides directed towards the eye. In order to secure the best possible definition with this form of eye-piece, the 
focal lengths of the lenses ought to be in the proportion of three to one (see Fig. 42). In the positive eye-piece 
the focal lengths of the component lenses are nearly equal, and their curved sides are turned towards each 
other as represented in Fig. 42. For low powers and flat fields, the positive eye-piece may be employed with 
advantage, but as it is not perfectly achromatic, the negative eye-piece is used instead for the higher powers. 



Fig. 41. THE "pillar and 

CLAW " STAND. 

F, Finder ; F, Eye-piece ; 

G, Garden or Tall Stand. 




Fig. 42. eye-pieces. 
D, Diaphragm. 



ASTRONOMICAL INSTRUMENTS. Ill 



1 


1-i 


2 


2^ 


3 


^ 


4 


5 


6 


7 


8 


9 


10 


4-5 


3-9 


2-3 


1-8 


1-5 


13 


M 


0-9 


0-8 


0-7 


0-6 


0-5 


0-4 



In commeucing observations with a telescope, it is advisable that low powers should be first 
employed. These may be gradually increased until the limit governed by the aperture, and sometimes 
by the conditions of the atmosphere, is reached. The former is regulated very much by the object to be 
viewed, as the fainter it is, the less magnifying it will stand. For comets and nebulae, a higher power 
than about twenty on a three-inch telescope ought not to be employed, as in this case the greatest space- 
penetrating power that the instrument is capable of giving is required. For viewing the planets, all 
powers up to about sixty to each inch of aperture can be used, or not over 200 diameters for a three-inch 
object-glass. When observing double stars, a much higher proportion can often with advantage be 
applied, or as high as 100 per inch of aperture. In viewing these most interesting objects, a complete 
list of which is inserted along with the star charts at the end of the volume, it must be borne in mind 
that the separating power of an object-lens depends entirely on its diameter. The dividing power of 
telescopes of different sizes are as follows: — 

Diameter of telescope in inches. 
Will divide in seconds of arc, , 

In viewing exceedingly close double stars, it is highly necessary that the telescope should be accurately 
focussed. In order to do this with the utmost delicacy, the focus ought to be adjusted on a star known 
to be single, and of about the same magnitude and altitude as the double star to be observed. A 
good deal, too, depends on the state of the atmosphere, as it is only when the air is very steady 
that the finest views can be obtained. After sudden changes of temperature the air is usually very 
unsteady, and unfavourable for observation ; while on those nights when the atmosphere contains large 
quantities of moisture, the definition of objects is finest. Very often a slight haze takes the glare 
off bright objects, and enables a good deal of detail to be seen. In viewing the sun, care must 
be taken not to do so without proper protection. With instruments smaller than four inches in 
diameter, a dense neutral-tinted glass screwed over the eye-piece is all that is required ; but with larger 
telescopes this would not be sufficient. In this case a specially constructed solar eye-piece is necessary, 
by the use of which, only a very small quantity of the light from the object-glass passes through 
the eye-lens. 

In conclusion, the encouraging words of the Council of the Royal Astronomical Society should be 
remembered, that " every one who possesses an instrument has the power to mark out for himself a 
useful and honourable occupation for leisure hours, in which his labour shall be really valuable, if 
duly registered." 



CHAPTER X. 

EXPLANATION OF THE STAR CHARTS, ETO. 

"Thereon were figured earth, and sky, and sea, 
The ever circling sun, and full orb'd moon, 
And all the signs that crown the vault of heav'n ; 
Pleiads and Hyads, and Orion's might, 
And Arctos, call'd the Wain." — Homer. 

As mentioned in Chapter IX., the first accurate star catalogue was constructed by Hipparchus in the year 
128 B.C. This contained the positions of 1022 stars, which were afterwards revised by Ptolemy, and reduced 
by him to the epoch of 137 a.d. The positions of the stars in this celebrated catalogue were, as already stated, 
determined by means of the astrolabe at different distances from the meridian, a method which is totally 
different from the modern one of meridional observations. At present, we have found, the positions of celestial 
objects are determined by means of the transit circle, and sidereal clock. From the instant of meridian passage, 
the right ascension is known, as it is simply the distance in time, as indicated by the sidereal clock, from the 
first point of Aries, measured on the equator ; while the declination, or distance in degrees from the equator, 
measured northwards and southwards, is determined by the altitude of the object, as indicated on the large 
graduated circle attached to the axis of the instrument. 

By means of these two important celestial co-ordinates, which correspond to the geographical co-ordinates 
of longitude and latitude, the position that each object occupies in the heavens is accurately fixed, and, at the 
same time, identified irrespective of its name or symbol. Before the time of Hipparchus, or the time 
when the positions of stars were first accurately determined with respect to some part of the star-sphere, such 
as the ecliptic or the equator, the various orbs were identified solely by the position they occupied in the 
group or constellation to which they belonged. Accordingly, the more numerous the constellations into 
which the heavens was divided, and the more accurately these were defined, the easier could the stars be 
identified. Though the star-sphere of the ancients probably contained a great many constellations, Ptolemy, 
in his celebrated work, the AVmegest, published about the year 150 A.D., only mentions forty-eight of them. 
These are known as the old constellations, most of which were familiar to Eudoxus, and are mentioned in 
Aratos as having been known at a very remote age {see Chapter I.). These constellations, as given in the 
Table on the opposite page, were, till within the last three hundred years, the only ones employed in dividing 
the stars into groups. Tycho was the first, in comparatively recent times, to invent new constellations, and 
this soon led other astronomers to carry out the idea to an absurd extent. The modern constellations, and the 
dates of their invention, are given in the Table, but many of them are not now used by astronomers, only the 
more important having been retained. 

DESIGNATION OF INDIVIDUAL STARS. 

Previous to the time of Bayer, the individual stars were identified by the positions they occupied in the 

constellations the brighter ones receiving special names to accurately denote this position, as for example Rds- 
112 



THE OLDEST KNOWN CONSTELLATIONS. 



Northern Constellations. 


Andromeda, .... The Chained Lady. 


Hercules, .... The Kneelinc Man. 1 


Aquila, . 






The Eagle. 


Lyra, 






. The Harp. 


Auriga, . 






. The Charioteei'. 


Ophiuchus, 






. The Serpent-Bearer. 


Bootes, . 






The Herdsman. 


Pegasus, . 






. Tlie Flying Horse. 


Cassiopeia, 






. The Lady in her Chair. 


Perseus, . 






. The Bescuer. 


Cepheus, . 






King Cepheus. 


Sagitta, . 






. The Arrow. 


Corona Borealis, 






The Northern Crown. 


Serpens, . 






. The Serpent. 


Cygnus, . 






The Swan. 


Triangulum, 






. The Triangle. 


Delphinus, 






The Dolphin. 


Ursa Major, 






. The Great Bear. 


Draco, 






The Dragon. 


Ursa Minor, 






. The Little Bear. 


Equuleus, 






. The Little Horse. 


1 


Southern Constellations. 


Ara, The Altar. 


Crater, The Cup. I 


Argo, 






The Ship Argo. 


Eridanus, 






. The River. 


Canis Major, . 






The Great Dog. 


Hydra, . 






. The Snake. 


Canis Minor, . 






The Little Dog. 


Lepus, 






. The Hare. 


Centaurus, 






The Centaur. 


Lupus, 






. The Wolf. 


Cetus, 






The Sea Monster. 


Orion, 






. The Hunter. 


Corona Australis, 




The Southern Crown. 


Piscis Australis, 




. The Southern Fish. 


CORVUS, . 




The Crow. 




Zodiacal Constellations. 


Aries, The Ram. 


Libra, The Balance. I 


Taurus, . 






The Bull. 


Scorpio, . 




. The Scoi-piou. 


Gemini, . 






The Twins. 


Sagittarius, 




. The Archer. 


Cancer, . 






The Crab. 


Capricornus, 




. The Goat. 


Leo, . 






The Lion. 


Aquarius, 




. The Water-Bearer. 


Virgo, 






. The Virgin. 


Pisces, 




. The Fishe?. 



THE MODERN CONSTELLATIONS. 



Name of Constellation. 


By whom Invented. 


Date v)hen 
added. 


Name of Constellation. 


By wliom Invented. 


Date when 
added. 


Antinous, .... 


Tycho Brahe, 


1603 A.D. 


Cor Caroli, .... 


Flamsteed, . 


1725 AD. 


Coma Bkrenices, . 






)» 


,, • 


MoNS Maenalus, . 




)» 


11 


Apis, 






Bayer, 


1604 


Antlia, . 




La Caille, . 


1752 


Avis Indica, . 






11 


„ 


Caeda Sculptorts, 




11 


11 


Chamasleon,. 






1) 


11 


CiRCINUS, 




11 


1? 


Dorado,. 






1) • 




Fornax,. 




11 • 


)? 


Grus, 






11 


11 


Horologium, . 




11 


J) 


Hydrus,. 






11 




Equuleus Pictoris, 




11 


1) 


Indus, . 






^J 


n 


Microscopium, 




11 


1) 


Phoknix, 






11 


11 


MoNS Mensae, 




11 


11 


Piscis Volans, 






11 * 


)) 


Norma, . 




11 


)> 


Pavo, 






1J • 


11 


OCTANS, . 




11 


)> 


Toucan, . 






11 • 


11 


Reticulum, . 




11 


11 


Triangulum Australe 










Sculptor, 




11 


11 


Camelopardalis, . 






Helvelius, . 


1690 


Pixis Nautica, 




11 


>t 


Canics Venatici, . 






5) • 


)) 


Telescopicm, 




„ 




Cerberus, 






J» ' 


11 


Solitarius, . 




Le Monnier, 


1776 


Lacerta, 






)J • 


Jl 


Tarandus, 




)) 


1* 


Leo Minor, . 






11 • 


)1 


Messier, 




Lalande, 




Lynx, 








11 


Taurus Poniatowskii, 




Poczobut, . 


1777 


Monoceros, . 






1) 


11 


P'elis, 




Bode, 


1800 


Sucutum, 






J) 


11 


Globus Aijrostaticcs, 




11 


J> 


Sextans, 






1) • 


jl 


Honores Fkederici, 




11 


» 


VULPECULA, . 






11 




LocHiL'.M Funis, . 








Columba Noachi, . 






Royer, 


1679 


M.vchina Klecthic.v, 


. 


„ 


» 


Crux, . 






1) 


;) 


Officina Typographica, 


» 


» 


Fleur-de-Lis, 






») 


^■f 


Quadrans IMuualis, 


)? 


?> 


NuBis Major, 






)J 


51 


SCEPTRUM BraNDENBURGICUM, 


)> 


5) 


Nubis Minor, 






51 • 


11 


Telescopicm Herschellii, . 


)) 




RoBUR Caroli, 






Halley, 


1680 









113 



114 



J POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



al-gdthi, the Kneeler's Head. By this means nearly every star could be described, for even those which were 
situated outside of the constellation were designated in a similar manner by their alignments with the brighter 
stars of the surrounding groups. In 1603 this cumbersome method was superseded by the elegant invention of 
Bayer, which has been found so convenient for the more important stars that it still remains in general use. 
This invention consisted in calling the stars in each constellation after some letter in the Greek alphabet, the 
sequence of the letters depending on the position of the stars in the constellation figure. Thus the seven stars 
in the " Plough," beginning with the one nearest to the pole, are designated a, /S, 7, S, e, ^, r]. In this manner 
the stars in each constellation are identified, until all the Greek letters are exhausted, when Roman letters are 
employed in continuation ; and, finally, when these fail, numbers are assigned instead. Flamsteed, the first 
Astronomer Royal at Greenwich, used numbers entirely for the stars in the constellations which he observed. 
Accordingly every star visible to the naked eye can be referred to, and at once identified either by a name, 
letter, or number, and sometimes by all of these. The principal star in Taurus, for instance, could be referred 
to as Aldebaran, a Tauri, or 87 (Flamsteed), of the same constellation ; while it could also be identified by its 
number in some standard star catalogue, so that 1420 B.A.C. and 8639 LI. indicates the same star, these 
being its number in the British Association and Lalande catalogues respectively. There are still other 
methods employed by modern astronomers for the purpose of identifying stars — viz., of arranging them into 
zones and numbering them accordingly. Piazzi adopted the method of numbering the stars according 



THE GEEEK ALPHABET. 



letter. Name. 

a Alpha 

B Beta 

7 Gamma 

S Delta 

e Epsilon 

f Zeta 



Letter. 



iS^me. 



17 Eta 

d Theta 

L Iota 

K Kappa 

\ Lambda 

/i Mu 



letter. 



Kame. 



V Nu 

^ Xi 

micron 

TT Pi 

p Rho 

(T Sigma 



Letter. Kame. 

T Tau 

V Upsilon 

4> Phi 

X Chi 

y^ Psi 

0) Omega 



to the position they occupy in the hour of right ascension, while in the large catalogue of Argelander's, called 
the " Durchmusterung," which contains no less than 324,000 stars, the stars are arranged and numbered in 
zones of declination one degree in breadth, and therefore Aldebaran could further be designated, P. iv. 125, 
andD.M. + 16°629. 

MAGNITUDES OF STARS. 

The relative amount of light which is received from a star, or its apparent brilliancy, is termed its magni- 
tude. The scale by means of which this was first determined was invented by Hipparchus. It consisted in 
dividing the stars visible to the unaided eye, from the brightest to the faintest, into six classes. The small 
group of brightest orbs were designated stars of the first magnitude, the next in brilliancy, stars of the second 
magnitude, until the faintest or sixth magnitude stars Avere reached. As there are many stars whose brilliancy 
lies midway between two whole magnitudes, a finer scale was necessary, and accordingly the magnitude of the 
stars in the catalogues of Hipparchus and Ptolemy were further divided into thirds. For a considerable time 
after Ptolemy, the more accurate method of arranging the stars into thirds of magnitude was abandoned, and it 
was only resumed in comparatively modern times. This method, which was adopted by Flamsteed, Argelander, 
Heis, and others, is as delicate a sub-division of stellar lights as the unaided eye is capable of distinguishing. 
It consists in first recording the stars belonging to the different whole magnitudes, then noting the other stars 
which are nearest in brightness to these. The various magnitudes and thirds of a magnitude are indicated 
as follows, the magnitude to which the star is nearest being placed first : — 



EXPLANATION OF THE STAR CHARTS, ETC. 



115 



Whole magnitudes, 




1 


2 


3 


4 


5 


6 


One-third of a magnitude, . 


. 


1,2 


2,3 


3,4 


4,5 


5,6 


6,7 


Two-thirds of a magnitude, 


. 


2,1 


3,2 


4,3 


5,4 


6,5 


7,6 


Accordingly 1,2 means IJ; 2,1, 1| 


, &c. 















Since the employment of instruments for the determination of stellar magnitudes this scale of thirds has 
been discarded, and the more minute system of decimals used instead. In the modem determinations, there- 
fore, the magnitudes of stars are given to the nearest tenth, the fractional part increasing as the brightness of 
the star diminishes; so that 1-2 magnitude indicates that the particular star is slightly brighter than one with 
a magnitude of 1'3. Similarly, a star whose magnitude is indicated by 0-5 is brighter than one whose magni- 
tude is 1"0, while the magnitude of Sirius, the brightest star in the heavens, is represented by — l-^, thereby 
meaning that it is more than a whole magnitude brighter than a star with a magnitude of 00. The number 
of stars in the various magnitudes visible to the unaided eye are as follows : — 



MAGNITUDE. 


NUMBER OF STARS. 


MAGNITUDE. 


NUMBER OF STARS. 


0-0 to 1-5 


21 


4-1 to 4-5 


316 


1-6 „ 20 


27 


4-6 „ 5-0 


446 


2-1 „ 2-5 


41 


5-1 „ 5-5 


937 


2-6 „ 3-0 


71 


5-6 „ 6-0 


1884 


31 „ 3-5 
3-6 „ 40 


138 

195 


6-1 „ 6-5 


2908 


Total, 6994 



STAR CHARTS. 

The very ancient astronomers were doubtless accustomed to depict the appearance of the starry heavens 
either on maps or on the surface of spheres of stone or metal. The earliest known instance of the constella- 
tions having been represented in this manner is the celebrated sphere of Eudoxos, constructed four centuries 
before our era (see Fig. 1). On this celestial globe, as on the modern ones, the constellations are reversed, as 
the eye of the observer is supposed to be placed in the centre of the sphere. This method of depicting the 
heavens was also adopted in the construction of star charts, and it was only as recent as the year 1603 that the 
more convenient and natural plan of representing the actual appearance of the star groups as seen from 
the earth, was adopted by Bayer. By this means the celestial maps could be compared directly with the starry 
sky, which had a considerable advantage over the fictitious outer surface of the imaginary celestial sphere. 

This is the method adopted in the star charts inserted at the end of the volume. The projection which has 
been employed in their construction is the one best suited to represent the appearance of the various star groups 
Avith the least possible distortion. By means of the twelve maps, the complete celestial sphere is depicted on a 
sufficiently large scale to enable the observer to readily identify even the faintest star indicated. To ensure 
the identification of objects being carried out with the greatest amount of ease, and to prevent the confusion 
which often arises when a constellation happens to be situated near the edge of a chart, each map has been 
constructed so as to represent more than a twelfth portion of the star-sphere. Accordingly, those constellations 
placed round the sides of the maps are indicated on at least two charts. This overlapping is especially 
valuable for clearly depicting the equatorial regions, as by it a zone extending to ten degrees on either side of 
the equator is doubly represented. 

In constructing these charts, the constellation figures were not inserted, as they only tend to confuse the 
observer, without increasing the value of the maps. The positions, however, which the constellations occupy 
are clearly indicated by the boundary lines which enclose the stars belonging to the diflerent groups. Only 



116 



A POPULAR HANDBOOK AND ATLAS OF ASTRONOMY. 



the more important of the constellations have been inserted, as many of those added within recent times 
are not recognised by astronomers. An alphabetical list of those used in the charts, with the number of stars 
in eacb, is given on pages 118 and 119; by means of which the number of the chart or circular map in 
which a constellation will be found, can be readily obtained. 

In .these charts, which contain more than 6000 objects, the stars are designated in the usual manner. 
Where a star has a Greek or Roman letter, it has been inserted, and if not, the Flamsteed number has been 
affixed instead. For the use of those desiring the accurate position of a star, the Table of Right Ascensions 
and Declinations of stars for the year 1890 is given on pages 127 to 135. The more important variable 
stars, double stars, nebulae, and star clusters are also inserted, which it is hoped will be of some value to 
those possessing small telescopes. The manner in which these objects are indicated is represented in Fig. 43. 
Accompanying the maps, a description will be found of the more interesting celestial objects visible with a 
telescope of moderate power. 

In using the maps the small circular charts will be of the greatest assistance, as by their aid the position 
which a particular constellation occupies with respect to the horizon can be ascertained for any required 
time. The circular maps are so constructed that they accurately represent the actual appearance of the 
heavens in the northern and southern hemispheres for certain times. Accordingly, the exact positions of the 
various constellations for any date and hour can be at once found by examining Tables 5 and 6 on pages 122 to 
125. From these, the corresponding circular chart is ascertained which represents the appearance of the star- 
sphere for the required time, and by means of the figures indicated in these maps, the large chart which corre- 




FiG. 43.— Explanation of the Star Charts. 

sponds to the particular part of the sky which it is desired to examine is also revealed. If, on the other 
hand, the time is required when a certain group can be seen. Table 1 on pages 118 and 119 will give the 
information. By its aid the circular chart which contains the constellation can at once be found ; when by 
referring to the particular map the time at which it is visible is indicated. 

The large scale plate. Chart 13, has been constructed so as to give a complete view of the zodiacal and equa- 
torial regions, and will thus be of great use for those who desire to follow the movements of the more conspicu- 
ous planets among the stars. This will be greatly facilitated by the heliocentric paths of the planets being 
indicated, or their apparent paths as viewed from the sun. By means of the right ascension and declination 
lines the position (obtained from an almanac) of a planet, comet, or other heavenly body, can be marked on the 
chart, and by noting the surrounding stars, easily identified. 

As it is often desirable to ascertain the time of sunrise and sunset, and the approximate duration of 
twilight, in order to know w^hen the faintest stars can be seen, the Tables inserted on pages 120 and 121 
have been constructed. By means of these Tables this information can be found without much difficulty, for 
any part of the globe, and any time of the year. From Table 2, in a line with the required date, 



^.JJL '^' ^°°^ ^ '^ ■^ »«,„ 





.J 

o 

O 

E- 
Oi 

< 
X 




■o liours jn UjoJ'""'" 



EXPLANATION OF TEE STAB CHARTS, ETC. 117 



and in the column indicated by the particular latitude of the place of observation, the hours and 
minutes of semi-diurnal arc will be found. This is equal to the apparent time of sunset, or of sunrise if 
subtracted from twelve hours. To find the true local mean time, the correction of equation of time in Table 
3 is to be applied to the apparent time of sunrise and sunset already ascertained. Then, lastly, the duration 
of twilight can be found from Table 4, which, when applied to the time of sunrise and sunset, gives the 
ending and beginning, respectively, of total darkness. 

Thus, for example, suppose it is desired to know the time of sunrise and sunset on 22nd October, for 
north latitude 55 degrees. Take from Table 2 the semi-diurnal arc corresponding to this date and latitude. 
This will be found to be 4h. 56m., which is equal to the apparent time of sunset for the date mentioned ; or, 
if subtracted from 12h., gives 7h. 4m. for the apparent time of sunrise. To find the equivalent mean time, the 
equation of time found in Table 3 is to be applied. For the above date this is — 15m. ; so that this quantity 
has to be subtracted from the apparent times already ascertained, when the true local raean time of sun- 
rising and sun-setting, become respectively, 6h. 49 A.M., and 4h. 43m. p.m. Lastly, from Table 4, the duration 
of twilight is found to be 2h. 10m., which, when subtracted from the time of sunrise, and added to the time 
of sunset, gives 4h. 39m. a.m., and 6h. 51m., p.m. for the time of the ending (in the morning) and beginning 
(in the evening) of total darkness. For ascertaining the time of a stair's rising, setting, and meridian passage, 
see Tables 7 and 8, which have been constructed to give this information with the least amount of trouble. 

As above mentioned, the times of sunrise and sunset thus determined are according to local mean time, 
or only for the time at the place for which they have been calculated. If, therefore, these local times are 
required to be converted into the mean time of any other meridian (as into Greenwich mean time), then the 
difference of longitude in time between the two places must be applied. If, for instance, the place for which 
the time of sunrise and sunset be required, is to the west of the meridian of the place whose time is 
employed (as in the case of Edinburgh from Greenwich), then the difference of longitude has to be added to 
the local time ; and if to the east, subtracted. From the Chart of the World, Plate 20, the difference of 
longitude in time between any two meridians, as well as the latitude of any place, can be ascertained. This 
Plate has been specially constructed on the Stereographic Projection, as it is one which recommends itself to 
the student for the many elegant and valuable properties which it possesses. On this projection, as is well 
known, all circles, great or small, with the exception of those which pass directly through the centre of 
projection, are projected into true circles; while all intersecting lines on the sphere are projected into lines 
intersecting on the Chait at exactly the same angle. Accordingly, in determining on the Chart the position 
of any circle of the sphere, unlike several other projections, only three points require to be projected, and the 
circle drawn through these points is the true projection of the circle. 



TABLE 1.— LIST OF THE CONSTELLATIONS INDICATED IN THE STAR CHARTS, 

And the Principal Charts in which each occurs. 

{N-ofc.—In the third Column, " Nos. 8 to 3" means Nos. 8, 9, 10, 11, 12, 1,2,3; " 23 «o 14 " means 23, 24, 13, 14 ; and similarly for other numlers). 





CHARTS IN WHICH THE CONSTELLATION IS INSERTED. 


Number of Stars in the Constellation. 


NAME OF CONSTELLATION. 


Large Star Charts. 


Small Circular Maps. 
N. Hemisphere. S. Hemisphere. 


Shown in the 
Charts. 


In Flamsteed's 
Catalogue. 




Nos. 


Nos. 






Andromeda, 


2, 13 


8 to 3 and 22 to 13 


95 


66 


Antlia, 


9 


22 to 18 


28 


3 


Apus, . 


12 


13 to 24 


22 


11 


Aquarius, . 


11, 13 


8 to 12 and 20 to 24 


117 


108 


Aquila, 


6, 10,-11, 13 


6 to 11 


91 


71 


Ara, .... 


10, 12 


13 to 24 


62 


9 


Argo, ^ 










(Carina, IMalus, V . 


8, 12 


22 to 18 


363 


64 


Puppis, Vela),J 










Aries, 


2, 13 


9 to 3 and 23 to 14 


52 


66 


Auriga, 


3, 13 


10 to 5 and 13 to 14 


72 


66 


Bootes, 


5, 13 


3 to 9 and 17 to 20 


107 


54 


CCELUM, 


7 


22 to 17 


25 


... 


Camelopardaijs, 


1 


1 tol2 


117 


58 


Cancer, 


4, 13 


1 to 6 and 13 to 17 


62 


83 


Canes Venatici, 


5 


1 to 12 


40 


25 


Canis Ma.ior, . 


8 


1 to 3 and 23 to 17 


73 


31 


Canis Minor, . 


4,13 


11 to 5 and 13 to 17 


25 


14 


Capricornus, 


11, 13 


8 to 10 and 19 to 24 


60 


51 


Cassiopeia, 


1 


1 to 12 


101 


55 


Centaurus, 


9, 12, and 13 


14 to 22 • 


184 


35 


Cepheus, . 


1 


1 to 12 


97 


35 


Cetus, 


7, 13 


10 to 2 and 21 to 13 


108 


97 


Chaji^ileon, 


12 


13 to 24 


36 


. 10 


Circinus, . 


12 


13 to 24 


11 


4 


COLUMBA, . 


8 


22 to 17 


65 


10 


Coma Bernices, . 


5 


3 to 8 and 16 to 19 


50 


43 


Corona Australis, . 


10 


17 to 23 


26 


12 


Corona Borealis, 


5 


17 to 20 


29 


21 


CORVUS, 


9, 13 


4 to 6 and 14 to 19 


12 


9 


Crater, 


9, 13 


3 to 6 and 14 to 19 


13 


31 


Crux,. 


12 


13 to 24 


16 


6 


Cygnus, 


6 


5 to 1 and 20 to 22 


159 


81 


Delphinus, 


6 


7 to 12 and 19 to 23 


17 


18 


Dorado, 


8 


13 to 24 


55 


7 


Draco, 


1 


1 to 12 


162 


80 


Equuleus, . 


6, 13 


7 to 12 and 19 to 23 


11 


10 


Eridanus, . 


7, 13 


11 to 2 and 21 to 16 


148 


84 


Fornax, 


7 


21 to 16 


58 


14 


Gemini, 


3, 13 


11 to 5 and 13 to 16 


64 


85 


Grus, . 


12 


13 to 24 


68 


13 


Hercules, . 


6, 13 


4 to 10 and 18 to 20 


140 


113 


HOROLOGIUM, 


12, 7 


13 to 24 


50 


12 



118 



LIST OF THE CONSTELLATIONS INDICATED IN THE STAR CE ARTS— continued. 





CHARTS IN WHICH THE CONSTELLATION IS INSERTED. 


Number of Stai;s in the Constellation. 


NAME OF CONSTELLATION. 


Large Star CHAnra. 


Small Circular Maps. 
N. Hemisphere. S. Hemisphere. 


Shovm in the 
Charts. 


In Flamsteid's 
Catalogue. 




Nos. 


Nos. 






Hydra, 


8, 9, 13 


2 to 6 and 13 to 18 


118 


60 


Hydrus, 






12 


13 to 24 


57 


10 


Indus, 






12 


13 to 24 


61 


12 


Lacerta, . 






2 


5 to 1 


36 


16 


Leo, . 






4,13 


2 to 7 and 15 to 18 


94 


95 


Leo Minor, 






4,13 


1 to 7 and 15 to 18 


32 


53 


Lepus, 






8 


11 to 3 and 23 to 17 


31 


19 


Libra, 






10, 13 


5 to 8 and 16 to 21 


53 


51 


Lupus, 






10, 12, 13 


14 to 22 


61 


24 


Lynx, 






4,13 


1 to 12 


46 


44 


Lyra, 






6 


5 to 12 and 19 to 21 


43 


22 


Mensa, 






12 


13 to 24 


28 


30 


MiCROSCOPIUM, 






11, 13 


13 to 24 


15 


10 


Monocebos, 






8, 13 


13 to 24 


46 


31 


MUSCA, 






12 


13 to 24 


35 


4 


Norma, 






10,12 


14 to 22 


48 


12 


OCTANS, 






12 


13 to 24 


55 


43 


Ophiuchus, 






10, 6, 13 


5 to 9 and 17 to 21 


93 


74 


Orion, 






3, 13 


11 to 4 and 23 to 16 


83 


78 


Pavo, 






12 


13 to 24 


106 


14 


Pegasus, . 






2,13 


8 to 1 and 21 to 24 


94 


89 


Perseus, 






3, 13 


9 to 5 and 24 and 13 


70 


89 


Ph(ENIX, 






12, 7 


13 to 24 


86 


13 


PiCTOR, 






12, 8 


22 to 17 


37 


16 


Pisces, 






2, 13 


9 to 2 and 22 to 13 


109 


113 


Piscis Australis 






11, 13 


10 to 11 and 19 to 13 


27 


24 


Reticulum, 






12 


13 to 24 


26 


10 


Sagitta, 






6 


6 to 12 


20 


18 


Sagittarius, 






10, 13 


7 to 9 and 17 to 23 


115 


69 


Scorpio, 






10, 13 


6 to 8 and 16 to 22 


90 


44 


Sculptor, . 






7,13 


21 to 13 


52 


12 


Serpens, . 






5, 6, 13 


5 to 10 and 17 to 21 


59 


64 


Sextans, . 






9, 13 


2 to 7 and 15 to 18 


30 


41 


Taurus, 






3, 13 


10 to 4 and 23 to 15 


127 


141 


Telescopium, 






10 


17 to 23 


19 


9 


Toucan, 






12 


13 to 24 


78 


9 1 


Triangulum, 






2, 13 


9 to 3 and 23 to 13 


27 


11 


Triangulum i 
Australe, f 




12 


13 to 24 


14 


5 


Ursa Major, 




1,13 


1 to 12 


122 


87 


Ursa Minor, 






1 


1 to 12 


40 


24 


Virgo, 






5, 9, 13 


3 to 7 and 15 to 19 


139 


110 


Volans, 






12 


13 to 24 


28 


8 


VULPECULA, 






6 


G to 12 


35 


37 



119 



Table 2. 
APPARENT TIME OF SUNRISE AND SUNSET AT DIFFERENT LATITUDES. 

The figures in the columns give the time of Sunset on the dates mentioned at the sides. To find the time of Sunrise, 
subtract the time of Sunset from 12 hours; the answer gives the time of Sunrise. {Seep. 117.) 



DATES FOR 




Time of Sunset for Latitude 


DATES FOR 


North Latitude. 




0° 10° 20° 30° 40° 45° 50° 55° 60° 


South Latitude. 






h 


m. 


h. m. 


h. m 


h. m. 


h. m. 


h. m. 


h. m. 


h. m 


h. m. 






December 21 


(21 


6 





5 42 


5 23 


5 2 


4 34 


4 17 


3 55 


3 24 


2 45 


June 21 


Junej^J 


/ 1 


December ■< 11 


6 





5 43 


5 24 


5 3 


4 37 


4 20 


3 58 


3 31 


2 51 


/ 2 


9 


( 2 


6 





5 44 


5 26 


5 6 


4 41 


4 25 


4 5 


3 39 


3 2 


11 




1 31 


January ( '^^ 


26 


6 





5 44 


5 28 


5 9 


4 45 


4 30 


4 11 


3 47 


3 13 


July<^ 18 




25 


^ \ 20 


21 


6 





5 45 


5 30 


5 11 


4 49 


4 35 


4 17 


3 55 


3 24 


23 




20 


24 


17 


6 





5 46 


5 31 


5 14 


4 53 


4 39 


4 23 


4 2 


3 34 


( 28 


May < 


16 


^28 


November < 13 


6 





5 47 


5 33 


5 17 


4 57 


4 44 


4 29 


4 10 


3 43 




1 


11 


/ 1 


9 


6 





5 48 


5 34 


5 19 


5 1 


4 49 


4 35 


4 16 


3 52 




5 




8 




4 


6 


6 





5 48 


5 36 


5 22 


5 4 


4 54 


4 40 


4 23 


4 1 




8 


4 




8 


^ 3 


6 





5 49 


5 38 


5 24 


5 8 


4 58 


4 46 


4 30 


4 9 




12 


1 




11 


/30 


6 





5 50 


5 39 


5 27 


5 12 


5 2 


4 51 


4 37 


4 18 




15 




27 


February / -. -- 




27 


6 





5 51 


5 41 


5 29 


5 15 


5 6 


4 56 


4 43 


4 26 


August ' 


18 




24 




25 


6 





5 51 


5 42 


5 32 


5 19 


5 11 


5 1 


4 50 


4 34 




21 




21 




19 




22 


6 





5 52 


5 44 


5 34 


5 22 


5 15 


5 6 


4 56 


4 41 




24 




18 




22 




19 


6 





5 53 


5 45 


5 37 


5 26 


5 20 


5 11 


5 2 


4 49 




27 


April < 


15 




25 


October^ 16 


6 





5 54 


5 47 


5 39 


5 29 


5 24 


5 16 


5 8 


4 56 




30 


13 


Us 




13 


6 





5 54 


5 48 


5 41 


5 33 


5 28 


5 21 


5 13 


5 4 


/ 2 




10 


/ 2 




11 


6 





5 55 


5 50 


5 44 


5 36 


5 32 


5 26 


5 19 


5 11 




4 




7 




5 




8 


6 





5 56 


5 51 


5 46 


5 40 


5 36 


5 31 


5 25 


5 18 




7 




5 




7 




5 


6 





5 56 


5 53 


5 48 


5 43 


5 40 


5 36 


5 31 


5 25 




10 




2 




10 


V 3 


6 





5 57 


5 54 


5 51 


5 47 


5 44 


5 41 


5 37 


5 32 




12 




/30 




13 


/30 


6 





5 58 


5 56 


5 53 


5 50 


5 48 


5 46 


5 42 


5 39 


15 

September/ ,» 




28 


March / -■ „ 




28 


6 





5 59 


5 57 


5 55 


5 53 


5 52 


5 50 


5 48 


5 46 




25 




25 


6 





5 59 


5 59 


5 58 


5 57 


5 56 


5 55 


5 54 


5 53 




20 




23 




20 




22 


6 





6 


6 


6 


6 


6 


6 


6 


6 




22 




20 




23 




20 


6 





6 1 


6 1 


6 2 


6 3 


6 4 


6 5 


6 6 


6 7 




25 


March i 


18 




25 


September .( ]\ 
\ 15 


6 





6 1 


6 3 


6 5 


6 7 


6 8 


6 10 


6 11 


6 14 




28 


15 


28 
^30 


6 





6 2 


6 4 


6 7 


6 10 


6 12 


6 14 


6 17 


6 21 


V30 




13 




12 


6 





6 3 


6 6 


6 9 


6 13 


6 16 


6 19 


6 23 


6 28 


, 3 




10 




r 2 




10 


6 





6 4 


6 7 


6 12 


6 17 


6 20 


6 24 


6 29 


6 35 




5 




7 




5 




7 


6 





6 4 


6 9 


6 14 


6 20 


6 24 


6 29 


6 35 


6 42 




8 




5 




7 




4 


6 





6 5 


6 10 


6 16 


6 24 


6 28 


6 34 


6 40 


6 49 




11 


V 2| 




10 


V 2 


6 





6 6 


6 12 


6 19 


6 27 


6 32 


6 39 


6 46 


6 56 




13 




28 


4nn-l ' '-^1 


'30 


6 





6 6 


6 13 


6 21 


6 31 


6 36 


6 44 


6 52 


7 4 


October < 16 




25 


April \ 


15 




27 


6 





6 7 


6 15 


6 23 


6 34 


6 41 


6 49 


6 58 


7 11 




19 




22 




18 




24 


6 





6 8 


6 16 


6 26 


6 38 


6 45 


6 54 


7 4 


7 19 




22 




19 




21 




21 


6 





6 9 


6 18 


6 28 


6 41 


6 49 


6 59 


7 11 


7 26 




25 


February < 


17 




24 


August < 


18 


6 





6 9 


6 19 


6 31 


6 45 


6 53 


7 4 


7 17 


7 34 




27 


14 


U7 


15 


6 





6 10 


6 21 


6 33 


6 48 


6 58 


7 9 


7 23 


7 42 


^ 30 




11 


1 




12 


6 





6 11 


6 22 


6 36 


6 52 


7 2 


7 14 


7 30 


7 51 


/ 3 




8 


4 




8 


6 





6 12 


6 24 


6 38 


6 56 


7 7 


7 20 


7 37 


7 59 


6 




4 


8 




5 


6 





6 12 


6 26 


6 41 


6 59 


7 11 


7 25 


7 44 


8 


9 




1 


May \ 11 




1 


6 





6 13 


6 27 


6 43 


7 3 


7 16 


7 31 


7 51 


8 17 


November < 13 


28 1 


* J \ 


lb 


28 


6 





6 14 


6 29 


6 46 


7 7 


7 21 


7 37 


7 58 


8 26 


17 




24 




20 


23 


6 





6 15 


6 30 


6 49 


7 11 


7 25 


7 43 


8 5 


8 36 


21 


January < 


20 




25 


July / 18 


6 





6 16 


6 32 


6 51 


7 15 


7 30 


7 49 


8 13 


8 47 


26 


15 


51 


11 


6 





6 16 


6 34 


6 54 


7 19 


7 35 


7 55 


8 21 


8 58 


( ^ 




9 


T f 10 

•June < m 


2 


6 





6 17 


6 36 


6 57 


7 23 


7 40 


8 2 


8 29 


9 9 


Decembers 11 


^ 1 


1 21 


June 21 


6 





6 18 


6 36 


6 58 


7 25 


7 43 


8 5 


8 33 


9 15 


(21 


December 2 1 


-iSk. ^^ 






















^ ^ 


liO 





































TABLE 3.— EQUATION OP TIME. 

On these dates the Minutes of Equation of Time are to he added to or subtracted from, as the case may he, the 
Apparent Time of Sunrise or Sunset as determined from Table 2. {See p. 117.) 



DA TE. 


Minutes 
To he To he 
Added. Subtkacied. 


DATE. T 
Ai 


Minutes 
be \ To be 
)DED, 1 Subtracted. 


DATE. 


Minutes 
To he 1 To be 
Added. | Subtracted. 


January 1 
4 


4 
5 






May 14 
28 




4 
3 


October 3 
6 






11 
12 


6 


6 






June 4 




2 


10 






13 


8 


7 






9 




1 


14 






14 


10 


8 






14 








17 






U"" 30« 


13 


9 






19 


1 




20 






15 


16 


10 






24 


2 




27 






16 


19 


11 






29 


3 




November 9 






16 


23 

27 


12 
13 






July 4 
10 


4 
5 




16 
19 






15 
U"" 30^ 


February 3 
10 


14 
U"" 30^ 






19 to 31 
August 2 


6 
6 




21 
24 






14 
13 


26 


13 






11 


5 




27 






12 


]\Iarcli 3 


12 






16 


4 




30 






11 


7 


11 






21 


3 




December 3 






10 


11 


10 






25 


2 




5 






9 


15 


9 






28 


1 




8 






8 


18 

22 


8 
7 






September 1 
4 






1 


10 
12 






7 
6 


25 


6 






7 




2 


14 






5 


28 


5 






10 




3 


16 






4 


April 1 
4 


4 
3 






13 
15 




4 
5 


18 
20 






3 

2 


7 


2 






18 




6 


22 






1 


11 


1 






21 




7 


24 








15 








24 




8 


27 


1 




20 




1 


27 




9 


29 


2 




25 




2 


30 


] 





31 


3 




30 




3 















TABLE 4.— DURATION OF TWILIGHT AT DIFFERENT LATITUDES. 



FOR NORTH LATITUDE 




FOR SOUTH LATITUDE 


At 
June Solstice. 


At ^^ 
(MarcTiZsept.). Deceraher Solstice. 


LATITUDE. 


At 
December Solstice. 


Ai 

Equinoxes 

(Sept. and March). 


At 
June Solstice. 


h. m. 


h. m. 


h. m. 




h. m. 


li. m. 


Ii. m. 


1 19 


1 12 


1 19 


0° 


1 19 


1 12 


1 19 


1 21 


1 13 


1 19 


10° 


1 21 


1 13 


1 19 


1 28 


1 17 


1 23 


20° 


1 28 


1 17 


1 23 


1 41 


1 24 


1 30 


30° 


1 41 


1 24 


1 30 


2 9 


1 35 


1 43 


40° 


2 9 


1 35 


1 43 


2 39 


1 44 


1 53 


45° 


2 39 


1 44 


1 53 


Twilight V 
extends from ) 


1 55 

2 10 


2 6 
2 26 


50° 
55° 


1 Twilight 
[ extends from 


1 55 

2 10 


2 6 
2 26 


sunset to J 
sunrise. 1 


2 33 

3 8 


2 57 
4 3 


60° 
65° 


( sunset to 
\ sunrise. 


2 33 

3 8 


2 57 
4 3 



121 



Table 5. 
FOR FINDING THE STARS VISIBLE IN THE NORTHERN HEMISPHERE, 

AT DIFFERENT DATES AND HOURS, BY MEANS OF THE CIRCULAR MAPS. 







January 




February 




March 






April 




Time. 




























5 


13 20 


27 


5 


13 20 


27 


7 


15 22 


29 


6 


14 21 


28 


4 h. m. 






11 








12 








1 








2 


... 


30 „ 




i'i 








i'2 


... 






i 








'2 


... 




5 h. m. 


ii 










i'2 




















2 


. 




... 




30 „ 




... 






12 










l' 










2 


... 


, 




... 


'3 


6 h. m. 






] 


L2 












.. . 














. 




3 




30 „ 




i'a 








... 








... 




2 












3 


... 


... 


7 h. m. 


12 


... 








1 








... 




... 








'3 


, 


. 




... 


30 „ 


... 








'i' 










2 




... 






3" 








... 


4 


8 h. m. 


... 








.., 


... 












... 






... 






. 


4 


... 


30 „ 




i 
















... 




3 










'4 


.., 


... 


9 h. m. 


i' 










2 




















'4 




. 


... 




30 „ 










2 










3" 










4 


.. . 




, 




5 


10 h. m. 




















... 












... 






'5 




30 „ 




2 




















'4 








... 


'5 






11 h. m. 


2 










'3 




















5 






... 




30 „ 










3 










4 




















6 


12 h. m. 




















. . . 


















'e 




30 „ 




3 




















'5 










'e 






*13 h. m. 


3 


• • . 








4 








... 




... 








6 








... 


30 „ 










4' 










5 




















7 


14 h. m. 


































. 




'7 


... 


30 „ 




4 




















'e 








... 


7 


... 


... 


15 h. m. 


4 










5 




















7 


, 


, 






30 „ 










5" 










6 




... 










, 


, 




8 


16 h. m. 


... 
































. 


, 


8 




30 „ 




5 






... 














■7 










8 


... 


..■ 


17 h. m. 


5 










'e 




















8 






... 




30 „ 


... 


... 






6 










i' 




... 










, 




... 


"9 


18 h. m. 




















... 


















9 




30 „ 




6 
















... 




8 










'9 




... 


19 h. m. 


6 








... 


7 




















'9 


, 


, 




... 


30 „ 










7 










8 










'9" 


... 


. 


. 




10 


20 h. m. 






7 








8 








9 


... 


... 


• 


• 


i6 


... 


Time. 




M AY 






June 






July 






August 






7 


15 22 


29 


6 


14 21 


28 


7 


15 22 


29 


6 


14 21 


28 


4 h. m. 






3 








4 








5 








6 




30 „ 




3 








4 








5 








6 






5 h. m. 


3 










'4 










'5 










6 








30 „ 










4' 










5" 










6 








7 


6 h. m. 








4 




















6 








'7 




30 „ 




4 








... 


5 










6 










7 






7 h. m. 


4 










5 


... 








6 










7 




... 




30 „ 










'5' 










6 










7 








8 


8 h. m. 


... 






5 




... 
















7 








8 




30 „ 




5 










6 




.. 






7 










8 






9 h. m. 


5 










6 










7 










8 








30 „ 










6 










7 










8 








9 


10 h. m. 








6 




















8 








9 




30 „ 




6 










7 










a 










9 






11 h. m. 


6 










7 










8 










9 








30 „ 










7 










8 










9 








16 


12 h. m. 








7 










8 










9 








16 




30 „ 




7 










8 










9 










io 






*13 h. m. 


7 










8 










'9 










io 








30 „ 










8 










9 










io 








ii 


14 h. m. 








8 










9 










l6 








ii 




30 „ 




8 










9 










i'6 










ii 






15 h. m. 


8 










9 










i'6 










ii 








30 „ 










9' 










16 










ii 








ii 


16 h. m. 








9 










l'6 










ii 








i2 




30 „ 




9 










16 










ii 










i'2 






17 h. m. 


9 










16 










ii 










i2 








30 „ 




. . . 






i'6 










ii 










i'2 








i' 


18 h. m. 






] 


l'6 








] 


LI 










12 








'i 




30 „ 




io 










ii 










i2 










i" 


.\ 




19 h. m. 


10 










ii 










i2 










i 








30 „ 










i'i 










i'2 










i' 








2 


20 h. m. 






11 


... 






i2 








1 


... 


... 


... 


'2 


... 1 



122 



TABLE 5, FOR THE NORTHERN REMl^PRERE— continued. 



Time. 


September 




October 




November 


December 


6 14 21 28 


6 


14 21 


28 


6 14 21 28 


6 14 21 


28 


4 h. m. 






7 








8 








9 








10 




30 ,, 


.. 


7 


... 


... 




8 








'9 








io 






5 h. m. 


7 


... 


... 




8 








'9 








io 


... 






30 „ 




... 




8 




... 


... 


'9 




... 




16 




... 




ii 


6 h. m. 




... 


8 








9 








io 








ii 




30 „ 




8 


... 






'9 


... 






i6 








ii 






7 h. m. 


8 








9 




... 




io 








ii 








30 „ 






... 


9 






... 


16 








11 








12 


8 h. m. 






9 








ib 








ii 








i2 




30 „ 




9 


... 






io 








ii 




... 




i'2 


. . . 




9 h. m. 


9 




... 




i'6 








ii 




... 




i'2 








30 „ 








i'6 








ii 








12 








i' 


10 h. m. 






i'6 








ii 








i2 


,. . 






i 




30 „ 




10 


... 






ii 








i'2 


... 






'i 






11 h. m. 


10 








li 


... 






i'2 








'i' 


... 






30 „ 








ii 




... 




i'2 




... 




i' 








2 


12 h. m. 






ii 








12 








'i 








'2 




30 „ 




ii 








i2 








'i 


... 






2 






* 13 h. m. 


ii 








i2 


... 






'i' 








'2 








30 „ 








12 




... 




i" 








'2' 








3 


14 h. m. 






i2 








i' 








'2 








'3 




30 „ 




12 






... 


i 








2 








3 






15 h. m. 


12 


... 






1 








2 








'3 








30 „ 








i' 








2' 








'3 








4' 


16 h. m. 




... 


i 


. . . 






2 


... 






3 


.. . 


... 




4 




30 „ 




1 


... 






2 


... 


... 




3 




*. . 


... 


'4 


... 




17 h. m. 


'i 








2 




... 


. 


3 




... 




4 




... 




30 „ 


... 






2 




... 




"3 








'4 








'5 


18 h. m. 


,, . 




2 






... 


'3 






, 


4 


... 






5 


... 


30 „ 




2 








'3 








4 ■ 




... 




'5 






19 h. m. 


2 


... 






'3 








■4 






... 


5 








30 „ 


t . . 






3 


... 






4' 








5" 








6 


20 h. m. 


... 




3 








'4 


... 


... 




'5 




... 




6 


... 



TABLE 5a. FOR ASCERTAINING THE TIME OF A STAR'S MERIDIAN PASSAGE. 



Eight AscENSIO^^ 
that is on the 


No. of 
Circular 

Map. 
N. S. 


Meridian. 


Oh. m. 


11 


23 


30 „ 
1 h. m. 


::: 


... 


30 „ 

2 h. m. 


i'2 


24 


30 „ 
3 h. m. 


... 


... 


30 „ 
4 h. m. 


T 


13 


30 „ 


... 


... 



Eight Ascension 

that is on the 

Meridian. 



5h. 
6h. 



7 h. 



8h. 



9h. 



Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 



No. of 

Circular 

Map. 

N. S. 



14 



15 



Eight Ascension 

that is on the 

Meridian. 



10 h. 



11 h. 

12 h. 

13 h. 

14 h. 



Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 



No. of 

Circular 

Map. 

N. S. 


4 


16 


5 


17 


6 


18 



Eight Ascensics 

that is 0)1 the 

Meridian. 



No. of 

Circular 

Map. 

1 N. S. 



15 h. 



16 h. 



17 h. 

18 h. 



19 h. 



m. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 

Om. 
30 „ 



19 



20 



Eight Ascension 

that is on the 

Meridian. 



20 h. Om. 

30 „ 

21 h. m. 

30 „ 

22 h. m. 

30 „ 

23 h. m. 

30 „ 
Oh. m. 



No. of 
Circular 
j Map. 
i N. S. 



21 



10 



11 



22 



23 



By means of Table 5, the positions of the stars above the horizon may readily be ascertained for any date and 
hour. The circular map, representing the appearance of the heavens for the required time, is given in the cohinm 
under the nearest date, and in the same line as the time indicated at the side. If the date cannot be found ■which 
will often happen, as four only for each m^nth are given, the one in the table nearest to the date required will 
indicate with sufficient accuracy the map representing the aspect of the starry sky. 

From the manner in which the circular maps are arranged, the approximate time at which any constellation 
or star culminates may also be ascertained. Knowing the Right Ascension of the object, which can be easily 
found from the large star charts, the small circular map, having this Right Ascension on the meridian, is given in 
Table 5a. Turning now to Table 5, the corresponding time will be found at the side opposite the number of the 
map indicated in the column of the given date. Suppose, for example, it is required to ascertain at what time the 
constellation of Aries crosses the meridian on the 6th of November. From the large cluirts, the Right Ascension 
of the group is found to be about two hours. This, in Table 5a, gives map 12, while in Table 5, in the column of 
6th November, and in a line with 12, will be found the corresponding time when the constellation of the Ram crosses 
the meridian. From Tables 7 and 8, on page 126, the time of a star's rising or setting may be ascertained. 

* NOTE.— In Astronomical reckoning, the day is divided into twenty-four hours, numbering from noon of the one day 
to noon of the next. At midnight, instead of being I., tl., 111. hours again as in Civil or Ordinary Tiiiio, nstrononiei-s 
continue the hours XIII., XIV., XV., and so on. Thus 4 p.m. is 4 hours, 1 a.m. is 13 hours, .'i A.^r. is 17 houi-s, &c. ; Noon 
is called hours minutes, or, contracted, h. m. 123 



Table 6. 
FOE. FINDING THE STARS VISIBLE IN THE SOUTHERN HEMISPHERE, 

AT DIFFERENT DATES AND HOURS, BY MEANS OF THE CIRCULAR MAPS. 



Time. 




January 


February 




March 






April 




5 


13 20 


27 


5 


13 20 


27 


7 


15 22 


29 


6 


14 21 


28 


4 h. m. 






23 








24 








13 








14 




30 „ 




23 








24 








is 








14 






5 h. m. 


23 








24 








13 








i'4 








30 „ 








24 








i's 








14 








i'5 


6 h. m. 






24 








is 








14 








i'5 




30 „ 




24 






... 


13 








14 








i'5 






7 h. m. 


24 








13 








i'4 








is 








30 „ 








13 








i4 








15 








ie 


8 h. m. 






is 




... 




14 








is 








i'e 




30 „ 




13 








14 








is 








i'e 






9 h. m. 


13 








14 








i's 








i'e 








30 „ 








14 








i'5 








ie 








17 


10 h. m. 






i4 


... 






is 








ie 








i'7 




30 „ 




14 








15 


... 






i'e 








i'7 






11 h. m. 


14 








i'5 








16 








i'7 








30 „ 








15 








ie 








17 








is 


12 h. m 






15 








16 








17 








18 




30 „ 




i'5 








i'e 








17 








i's 






*13 h. m. 


15 








i'e 








i'7 








18 








30 „ 








i'e 








l'7 








is 








ig 


14 h. m 






i'e 








i'7 








18 








19 




30 „ 




i'e 








17 








is 








i'g 






15 h. m. 


i'e 








17 








I's 








i'g 








30 „ 








i? 








is 








i'g 








2"6 


16 h. m 






17 








18 








19 








20 




30 „ 




17 








18 








i'g 








20 






17 h. m. 


l'7 








18 








i'9 








20 








30 „ 








18 








i'9 








20 








2i 


18 h. m. 






18 








19 








20 








ai 




30 „ 




18 








19 








20 








sii 






19 h. m. 


i's 


,.. 






i'g 








20 








2i 








30 „ 








19 








20 








21 








2'2 


20 h. m. 






19 








20 








21 








22 




Time. 




M AY 






June 






July 






August 




7 


15 22 


29 


6 


14 21 


28 


7 


15 22 


29 


6 


14 21 


28 


4 h. m. 






15 








16 








17 








18 




30 ,, 




i's 








i'e 








17 








18 






5 h. m. 


15 








16 








i'7 








i's 








30 „ 








i'e 








i'7 








18 








ig 


6 h. m. 






i'e 








i'7 








i's 








ig 




30 „ 




i'e 




... 




17 








is 








ig 






7 h. m. 


i'e 








17 








18 








i'g 








30 „ 








i7 








is 








i'g 








20 


8 h. m. 






17 








18 








ig 








20 




30 „ 




17 








is 








ig 








20 






9 h. m. 


l'7 








i'8 








ig 








20 








30 „ 








i's 








i'g 








20 








21 


10 h. m. 






18 








i'9 








20 








2'i 




30 „ 




i'8 








i9 








20 








2'i 






11 h. m. 


18 








i9 








20 








2i 








30 „ 








i'9 








20 








21 








2'2 


12 h. m. 






ig 








20 








2'i 








22 




30 „ 




ig 








20 








2i 








22 






M3 h. m. 


19 








20 








21 








22 








30 „ 








20 








21 








22 








2'3 


14 h. m. 






20 








ai 








22 








23 




30 „ 




20 








2'i 








22 








23 






15 h. m. 


20 








2'i 








2'2 








23 








30 „ 








21 








22 








2'3 








24 


16 h, m. 






2i 








22 








23 








24 




30 „ 




2i 








22 








23 








24 






17 h. m. 


21 








22 








23 








24 








30 „ 








22 








23 








24 








13 


18 h. m. 






22 








23 








24 








i's 




30 „ 




22 








23 








24 








i's 






19 h. m. 


22 








23 








24 








is 








30 „ 








23 








24 








13 








i4 


20 h. m. 




... 


23 








24 








is 








14 





124 



TABLE 6, FOR THE SOUTHERN HEMISPHERE — conimwed 



Time. 


Septem BER 




October 




N 


OVE 


M B ER 


D 


ECEM BE 


R 














6 14 21 28 


6 


14 21 


28 


6 


14 21 


28 


6 


14 21 


28 


4 h. m. 






19 








20 








21 








22 




30 „ 




19 


. . . 






20 


... 






2'i 








22 






5 h. m. 


i'9 




. . • 




20 




... 




2'i 




. . . 


... 


22 








30 „ 








20 








21 


... 






22 




... 




23 


6 h. m. 






20 








2i 


... 






22 








23 




30 „ 




20 








2i 




... 




22 








23 






7 h. m. 


20 


... 






21 








22 








23 








30 „ 




... 




21 








2'2 








23 








24 


8 h. m. 


... 




21 


... 






22 








23 








24 


... 


30 „ 




21 




... 


... 


22 








23 








24 






9 h. m. 


21 








22 


... 






23 








24 








30 „ 








22 




... 




2'3 








24 








is 


10 h. m. 




... 


22 








23 








24 


... 






13 




30 „ 


... 


22 








23 








24 








13 






11 h. m. 


22 


.. . 






23 




... 




24 








i's 








30 „ 








23 








24 








is 








i4 


12 h. m. 






23 


... 






24 








13 








i'4 




30 „ 




23 




... 




24 








i'3 








i'4 






*13 h. m. 


23 








24 








13 








14 








30 „ 








24 


... 


... 




13 








14 








15 


14 h. m. 






24 








13 








i'4 








15 




30 „ 




24 








13 


... 






14 








15 






15 h. m. 


24 








i's 








14 








15 








30 „ 








i's 


... 






14 








is 








i'e 


16 h. m. 






13 




... 




14 








i'5 


... 






i'e 




30 „ 




is 






. 


i'4 








i'5 








i'e 






17 h. m. 


13 








i'4 








i'5 








i'e 








30 „ 








14 








i's 








ie 








17 


18 h. m. 






14 








15 








i'e 








i'7 




30 „ 




i'4 








15 








ie 








17 






19 h. m. 


14 








i'5 








i'e 








17 








30 „ 








15 








i'e 








i'? 








18 


20 h. m. 




... 


15 




... 




l"6 








i'7 








is 





TABLE 6a. 


FOR ASCERTAINING THE TIME C 


IF 


A STAR'S MERIDIAN PASSAGE. 


Eight Ascension 

that is on the 

Meridian. 


No. of 

Circular 

Map. 

S. N. 


Eight Ascension 

that is on the 

Meridian. 


No. of 

Circular 

Map. 

S. N. 


Right Ascevsion 

that is on the 

Meridian. 


No. of 

Circular 

Map. 

S. N. 


Eight Ascension 

that is oil the 

Meridian. 


No. of 

Circular 

Map. 

S. N. 


Eight Ascension 

ihut is on the 

Meridian. 


No. of 

Circular 

Map. 

S. N. 


Oh. m. 
30 „ 

1 h. m. 

30 „ 

2 h. m. 

30 „ 

3 h. m. 

30 „ 

4 h. m. 

30 „ 


23 
24 
13 


11 
12 

i 


5 h. m. 

30 „ 

6 h. m. 

30 „ 

7 h. m. 

30 „ 

8 h. m. 

30 „ 

9 h. m. 

30 „ 


14 
15 


2 
3 


10 h. Om. 

30 „ 

11 h. Om. 

30 „ 

12 h. Om. 

30 „ 

13 h. m. 

30 „ 

14 h. Om. 

30 „ 


16 

iV 

18 


4 
5 
6 


15 h. m. 

30 „ 

16 h. m. 

30 „ 

17 h. m. 

30 „ 

18 h. Om. 

30 „ 

19 h. m. 

30 „ 


19 

20 


7 
8 


20 h. Om. 

30 „ 

21 L. m. 

30 „ 

22 h. m. 

30 „ 

23 h. m. 

30 „ 
h. m. 


21 
22 
23 


9 

i'6 

11 



By means of Table 6, the positions of the stars above the horizon may readily be ascertained for any date and 
hour. The circular map, representing the appearance of the heavens for the required time, is given in the cohmm 
under the nearest date, and in the same line as the time indicated at the side. If the date cannot be found which 
will often happen, as four only for each month are given, the one in the table nearest to the date required will 
indicate with sufficient accuracy the map representing the aspect of the starry sky. 

From the manner in which the circular maps are arranged, the approximate time at which any constellation 
or star culminates may also be ascertained. Knowing the Right Ascension of the object, which can be easily 
found from the large star cliarts, the small circular map, having this Right Ascension on the meridian, is given in 
Table 6a. Turning now to Table 6, the corresponding time will be found at the side opposite the number of the 
map indicated in the column of the given date. Suppose, for example, it is required to ascertain at what time the 
constellation of Aries crosses the meridian on the 6th of November. From the large charts, the Right Ascension 
of the group is found to be about two hours. This, in Table 6a, gives map 2-1:, while in Table 6, in the column of 
6th November, and in a line with 24, will be found the corresponding time when the constellation of the Ram crosses 
the meridian. From Tables 7 and 8, on page 126, the time of a star's rising or setting may be ascertained. 

* NOTE. — In Astronomical reckoning, the day is divided into twenty -four hours, numbering from noon of the one diiy 
to noon of the next. At midnight, instead of being I.. II., III. hours again as in Civil or Ordinary Time, astronomers 
continue the hours XIII., XIV., XV., and so on. Thus 4 p.m. is 4 hours, 1 a.m. is 13 hours, b a.m. is 17 hours, &c. ; Noon 
i§ called hours minutes, or, contracted, h. in. 125 

R 



TABLE 7.— SIDEREAL TIME, 

Or Hour and Minute of Right Ascension on the Meridian at Noon on the following dates : — 



Day 

OF THE 

Month. 


January. 


Feb. 


March. 


April. 


May. 


June. 


July. 


August. 


Sept. 


Oct. 


Nov. 


Dec. 


5 


h m. 

19 


h. m. 

21 2 


h. ni. 

22 53 


b. m. 

55 


h. m. 

2 53 


h. m. 

4 55 


h. m, 

6 54 


h. m. 

8 56 


h. m. 

10 58 


h. m. 

12 56 


h. m. 

14 59 


b. m. 

16 57 


10 


19 20 


21 22 


23 12 


1 15 


3 13 


5 15 


7 13 


9 16 


11 18 


13 16 


15 18 


17 17 


15 


19 40 


21 42 


23 32 


1 35 


3 33 


5 35 


7 33 


9 35 


11 38 


13 36 


15 38 


17 36 


20 


20 


22 1 


23 52 


1 54 


3 52 


5 55 


7 53 


9 55 


11 57 


13 56 


15 58 


17 56 


25 


20 19 


22 21 


12 


2 14 


4 12 


6 14 


8 13 


10 15 


12 17 


14 15 


16 18 


18 16 


30 


20 39 


... 


31 


2 34 


4 32 


6 34 


8 32 


10 35 


12 37 


14 35 


16 37 


18 36 










Fo 


■ Internudiate Dates add four minutes for each day. 









TABLE 8.— TIME BETWEEN A STAR'S RISING OR SETTING AND ITS 

CULMINATION. 



DECLINATION 
OF 














Star 


Rises 


. OR Sets 


after Culmination 


at 


Latitude. 








STAR. 






5° 


10° 


15° 


20° 


25° 


30° 


35° 


40° 


45' 


50° 


55° 


60° 






h. 


m. 


b. 


m. 


b. 


m. 


h. 


m. 


b. 


m. 


h. 


m. 


h, m. 


h. m. 


h. 


m. 


b. m. 


h. 


m. 


h. m. 


Declination of the same 
name as the Latitude 


30° 

25° 


6 
6 


11 

8 


6 
6 


23 
19 


6 
6 


36 

29 


6 
6 


49 
39 


7 
6 


2 
49 


7 

7 


19 

2 


7 35 
7 16 


7 55 
7 32 


8 

7 


18 

51 


8 53 

8 15 


9 

8 


39 

47 


11 22 
9 35 


of the place — i.e., if 


20° 


6 


7 


6 


15 


6 


22 


6 


30 


6 


39 


6 


49 


6 59 


7 11 


7 


25 


7 43 


8 


5 


8 36 


Lat. N. atid Dec. N., ^ 
or if Lat. S. and 
Dec.S. 


15° 
10° 


6 
6 


5 

4 


6 
6 


11 

7 


6 
6 


16 
11 


6 
6 


22 
15 


6 
6 


29 
19 


6 
6 


36 
23 


6 43 

6 28 


6 52 
6 34 


7 
6 


2 
41 


7 14 
6 49 


7 
6 


30 

58 


7 51 
7 11 




5° 


6 


2 


6 


4 


6 


5 


6 


7 


6 


9 


6 


12 


6 14 


6 17 


6 


20 


6 24 


6 


29 


6 35 




0° 


6 





6 





6 





6 





6 





6 





6 


6 


6 





6 


6 





6 


Declination o/ contrary 


5° 


5 


58 


5 


56 


5 


55 


5 


53 


5 


51 


5 


48 


5 46 


5 43 


5 


40 


5 36 


5 


31 


5 25 


name to the Latitude 


10° 


5 


56 


5 


53 


5 


49 


5 


45 


5 


41 


5 


37 


5 32 


5 26 


5 


19 


5 11 


5 


2 


4 49 


oj the place — i.e., if 
Lat. N and Dec S ^ 


15° 


5 


55 


5 


49 


5 


44 


5 


38 


5 


31 


5 


24 


5 17 


5 8 


4 


58 


4 46 


4 


30 


4 9 


or if Lat. S. and 


20° 


5 


53 


5 


45 


5 


38 


5 


30 


5 


21 


5 


11 


5 1 


4 49 


4 


35 


4 17 


3 


55 


3 24 


Dec. N. 


25° 


5 


52 


5 


41 


5 


31 


5 


21 


5 


11 


4 


58 


4 44 


4 28 


4 


9 


3 45 


3 


13 


2 25 




30° 


5 


49 


5 


37 


5 


24 


5 


11 


4 


58 


4 


41 


4 25 


4 5 


3 


42 


3 7 


2 


21 


38 



By means of the above Tables the approximate time of the rising and setting of a star may easily be found. The 
time of culminating, as already mentioned, can be roughly ascertained by aid of Tables 5a and 6a. This information, 
however, can be found with far greater accuracy from Table 7, which gives the sidereal time for different days 
throughout the year, or the hour and minute of Right Ascension that is on the meridian at noon. From tliis, the time 
of a star's meridian passage may be found very nearly, by simply subtracting the sidereal time for the date required 
from the star's Right Ascension. If, now, the number of hours and minutes found in Table 8 for the latitude of the 
place and the Declination of the star be added to, or subtracted from, the time of crossing the meridian, the approximate 
time of rising and setting will be ascertained. 

Suppose, for example, the time is required at which the bright star Frocyon rises, culminates, and sets on 
the 10th of January in latitude 50 degrees North. From the Table of the Positions of the Stars, on pages 127 
to 135, the Right Ascension of the star is found to be 7 h. 33 m., and the Declination 5° 30' N. ; while in Table 7 
the sidereal time for the given date is 19 h. 20 m. This has now to be subtracted from the Right Ascension of the 
star (to which 24 h. has to be added, as in this case the Right Ascension is less than the sidereal time), in order 
to ascertain the approximate time of meridian passage, which is 12 h. 13 m. Lastly, from Table 8, for latitude 
50° N., and Declination 5° N., the time at which the star rises before and sets after culmination, is found to 
be 6 h. 24 m. ; and this subtracted from 12 h. 13 m., the time of meridian passage, gives 5 h. 49 m. and 18 h, 37 m. 
for the rising and setting respectively. 
120 



TABLE 9.— THE NAMES AND POSITIONS OF THE MORE IMPORTANT STARS, 

REDUCED TO EPOCH OF 1890. 







Greek or Roman Letter, 


Flamsteed 






RIGHT 




No. 


CONSTELLATION. 


and Synonym. 


Number. 


B.A.C. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


1 


Andromeda, . 


a {Alpheratz), 


21 


4 


2-1 


h m. 8. 

2 42 


28' 28' 59" n. 


2 


Cassiopeia, 




l3{Chaph), . 


11 


7 


2-4 


3 18 


58' 32' 37" N. 


3 


Phcenix, . 




I,. 


... 


11 


3-9 


3 49 


46° 21' 14" s. 


4 


Pegasus, . 




y (Algenib), . 


88 


26 


30 


7 34 


14° 34' 19" N. 


5 


Cetus, . 




1 {Dheneb Kaitos), 


8 


62 


3-6 


13 49 


9' 26' 2"s. 


6 


Hydrus, . 




13, . . . 


... 


88 


2-8 


19 57 


77' 52' 26" s. 


7 


Phcenix, . 




X, . . . 


... 


93 


4-0 


20 47 


44' 17' 24" s. 


8 


Phcenix, . 




a, . . . 


... 


94 


2-4 


20 1 


42' 54' 10" s. 


9 


Cassiopeia, 




X, . . . 


15 


126 


4-2 


26 45 


62' 19' 30" N. 


10 


Cassiopeia, 




?. . . . 


17 


153 


3-7 


30 51 


53' 17' 31" N. 


11 


Andromeda, 




T, . . . 


29 


155 


4-3 


31 


33' 6' 51" N. 


12 


Andromeda, 




e, . . . 


30 


164 


4-6 


32 45 


28° 42' 57" N. 


13 


Andromeda, 




6, •. • • 


31 


166 


3-4 


33 27 


30' 15' 30" N. 


14 


Cassiopeia, 




a (Schedir), . 


18 


169 


2-2 


34 16 


55' 56' 2" N, 


15 


Cetus, . 




/3 {Diphda), . 


16 


196 


21 


38 4 


18° 35' 25" s. 


16 


Cassiopeia, 




>!,... 


24 


218 


3-6 


42 27 


57° 13' 56" N. 


17 


Cassiopeia, 




7, . . . 


27 


253 


2-3 


50 4 


60° 7' 17" N. 


18 


Andromeda, 




/*,... 


37 


259 


3-9 


50 39 


37° 54' 12" N. 


19 


Pisces, . 




£, . . . 


71 


288 


4-5 


57 14 


7° 17' 51" N. 


20 


Phcenix, . 




/3, . . . 


... 


317 


3-4 


1 1 10 


47° 18' 28" s. 


21 


Cetus, . 




>j {Dheneh), . 


31 


332 


3-6 


1 3 3 


10° 45' 54" s. 


22 


Andromeda, . 




jS (Mirach), . 


43 


334 


2-2 


1 3 34 


35' 2' 14" N. 


23 


Ursa Minor, . 




a (Polaris), , 


1 


360 


2-2 


1 18 29 


88° 43' 18" N. 


24 


Cassiopeia, 




d, . . . 


37 


416 


2-9 


1 18 37 


59° 39' 48" N. 


25 


Cetus, . 




6, . . . 


45 


420 


3-8 


1 18 31 


8° 45' 4" s. 


26 


Phcenix, . 




7, . . . 


... 


447 


3-5 


1 23 35 


43° 52' 43" s 


27 


Pisces, . 




SJj . . 


99 


453 


3-8 


1 25 .36 


14° 46' 42" N. 


28 


Andromeda, . 




V, ... 


51 


487 


3-7 


1 31 15 


48° 4' 14" N. 


29 


Eridanus, 




a (Achemar), 




507 


0-5 


1 33 37 


57° 47' 45" s. 


30 


Andromeda, . 




<p, . . . 


54 


522 


4-2 


1 36 46 


50°. 8' 2"n. 


31 


Cetus, 




r, . . . 


52 


536 


3-6 


1 38 58 


16° 30' 59" s. 


32 


Cassiopeia, 




£, ... 


45 


564 


3 6 


1 46 29 


63° 7' 42" N. 


33 


Cetus, . 




^ {Baten-kaitos), . 


55 


565 


3-9 


1 46 2 


10° 52' 49" s. 


34 


Triangula, 




cc, . . . 


2 


569 


3-6 


1 46 49 


29° 2' 37" N. 


35 
36 


Aries, 
Aries, 


} 


7 {Mesarthim), 


u 


572 ) 

573 J 


4-3 


1 47 30 


18' 45' 16" N. 


37 


Aries, 




(3 (Slieratan), 


6 


577 


2-8 


1 48 34 


20° 16' 12" N. 


38 


Eridanus, 




X' • ' ■ 


• • . 


596 


4-0 


1 51 40 


52° ir 27" s. 


39 


Cassiopeia, 






50 


600 


4-0 


1 54 3 


71° 53' 19" N. 


40 


Cetus, . 




V, . . . 


59 


618 


3-8 


1 54 49 


21° 36' 39" & 


41 


Hydrus, . 




«, . . . 




623 


3-0 


1 55 18 


62° 6' W'fL 


42 


Pisces, . 




a {Kaitdin), . 


113 


625 


4-0 


1 56 22 


2° 13' 58" X. 


43 


Andromeda, . 




7 (Almach), . 


57 


628 


2-2 


1 57 9 


41° 48' 7" N. 


44 


Aries, 




a (Hamal), . 


13 


648 


21 


2 58 


22' 56' 31" N. 


45 


Triangulum, . 




i3, . . . 


4 


656 


31 


2 3 


34° 28' 2" N. 


46 


Eridanus, 




<P> • 




717 


3-6 


2 12 34 


52' r 16" fi 


47 


Cetus, . 




(Mir a), 


68 


720 


Var. 2 to 7 


2 13 47 


3° 28' 4a' s. 


48 


Hydrus, . 




h, . . . 


• . . 


756 


4-2 


2 19 48 


69° 9' 56" s. 


49 


Cetus, . 




V, . . . 


73 


760 


4-5 


2 22 19 


7° 58' 0" N. 


50 


Cetus, . 




h, . . . 


82 


811 


4-1 


2 33 51 


0° 8' 50" s. 



\-21 



THE NAMES AND POSITIONS OF THE MOEE IMPOETANT STARS, kc— continued. 



Xo. 


COXSTELLATIOX. 


GreeJ; or Soman Letter, 
and Synonym. 


Flamsteed 
Number. 


BA.C. 


MAGNITUDE. 


RIGHT 
ASCENSION. 


DECLINATION. 


51 


Perseus, . 


i\ ... 


13 


827 


4-3 


h. m. s. 

2 36 41 


48° 45' 46" N. 


52 


Cetus, 




y (Kaff-al-jidhina), 


86 


837 


3-6 


2 37 36 


2° 46' 17" N. 


53 


Cetus, 




*) ' • * 


89 


847 


4-3 


2 38 53 


14° 19' 31" s. 


54 


Perseus, . 




r„ . . . 


15 


863 


4-0 


2 42 40 


55° 26' 19" N. 


55 


Aries, 






41 


872 


3-8 


2 43 30 


26° 48' 27" N. 


56 


Perseus, . 




T, . . . 


18 


885 


4-0 


2 46 28 


52° 18' 43" N. 


57 


Eridanus, 




n, . . . 


3 


910 


4-0 


2 51 3 


9° 20' 11" s. 


58 


Eridanus, 




0, . . . 




937 


2-7 


2 54 5 


40° 44' 34" s. 


59 


Perseus, . 




7> • ' • 


23 


947 


3-1 


2 56 50 


53° 4' 31" N. 


60 


Cetus, 




a, ... 


92 


949 


2-7 


2 56 32 


3° 39' 27" N. 


61 


Perseus, . 




e, . . . 


25 


953 


3-7 


2 58 8 


38° 24' 51" N. 


62 


Eridanus, 




r\ .. . . 


11 


954 


4-1 


2 57 33 


24° 3' 22" s. 


63 


Perseus, . 




/, ... 




962 


4-1 


3 1 7 


49° 11' 38" N. 


61 


Perseus, .• 




/? {Algol), . . 


26 


963 


2-3 


3 1 2 


40° 31' 54" N. 


65 


Aries, 




b, . . . 


57 


986 


4-5 


3 5 20 


19° 18' 37" N. 


66 


Eridanus, 






12 


997 


3-8 


3 7 23 


29° 25' 23" s. 


67 


Eridanus, 




^4 

* , . • 1 


16 


1037 


3-8 


3 14 37 


22° 9' 32" s. 


68 


Perseus, . 




a {Mirfak), . 


33 


1043 


2-0 


3 16 28 


49° 28' 8" N. 


69 


Taurus, . 




0, ... 


1 


1057 


3-8 


3 18 54 


8° 38' 24" N. 


70 


Taurus, . 




I, . . . 


2 


1068 


3-8 


3 21 13 


9° 20' 56" N. 


71 


Eridanus, 




£, ... 


18 


1100 


3-7 


3 27 45 


9° 49' 52" s. 


72 


Perseus, . 




6, . . . 


39 


1129 


3-2 


3 35 6 


47° 26' 7" N- 


73 


Perseus, . 




0, , . . 


38 


1138 


4-0 


3 37 25 


31° 56' 25" N. 


74 


Perseus, 




V, , . . 


41 


1139 


4-0 


3 37 43 


42° 13' 51" N. 


75 


Taurus, . 






17 


1147 


3-8 


3 38 21 


23° 46' 2"n. 


76 


Eridanus, 




h, . . . 


23 


1148 


3-7 


3 37 59 


10° 8' 12" s. 


77 


Taurus, , 




V, ■ ■ • 


25 


1166 


. 3-0 


3 40 57 


23° 45' 52" N. 


78 


Taurus, . 






27 


1176 


3-8 


3 42 37 


23° 43' 1"n. 


79 


Perseus, . 




I . . ■ 


44 


1207 


3-1 


3 47 13 


31° 33' 24" N. 


80 


Perseus, . 




s, ... 


45 


1219 


3-1 


3 50 28 


39° 41' 29" N. 


81 


Hydrus, . 




7, ■ ■ ■ 




1230 


3 3 


3 48 57 


74° 34' 32" s. 


82 


Eridanus, 




y (Zaurak), . 


34 


1234 


3-0 


3 52 54 


13° 49' 20" s. 


83 


Taurus, . 




}., ... 


35 


1241 


3-6 


3 54 35 


12° 10' 47" N. 


84 


Eridanus, 




o' (Beid), . 


38 


1290 


4-1 


4 6 30 


7° 7' 29" s. 


85 


Taurus, . 




y {HyadiimPrimus), 


54 


1328 


3-9 


4 13 32 


15° 21' 41" N. 


86 


Eridanus, 




A . . . 


41 


1333 


33 


4 13 43 


34° 4' 2"s. 


87 


Eeticulum, 




a, ... 




1336 


3-4 


4 12 59 


62° 44' 58" s. 


88 


Taurus, . 




b, . . . 


61 


1346 


4-0 


4 16 35 


17° 17' 3" N. 


89 


Eridanus, 




u^ . . . 


43 


1372 


4-0 


4 19 53 


34° 16' 22" 


90 


Taurus, . 




i, ... 


74 


1376 


3-7 


4 22 12 


18° 56' 9"n. 


91 


Taurus, . 




j; } {Alya), . . 


f 77 
(78 


1380 


3-9 


4 22 17 


15° 43' 4"n. 


92 


Taurus, . 




1381 


3-6 


4 21 15 


15° 34' 49" N. 


93 


Taurus, . 




a (Aldebaran), 


87 


1420 


1-0 


4 29 36 


16° 17' 15" N. 


94 


Eridanus, 




f, ... 


48 


1429 


3-9 


4 30 50 


3° 34' 39" s. 


95 


Eridanus, 




V-, 


52 


1433 


3-8 


4 31 16 


30° 47' 15" s. 


96 


Dorado, . 




a, . ... 




1438 


3-2 


4 31 37 


55° 16' 20" s. 


97 


Eridanus, 






53 


1441 


3-9 


4 33 9 


14° 31' 10" s. 


98 


Eridanus, 




//., ... 


57 ■ 


1469 


4-3 


4 40 


3° 27' 25" s. 


99 


Orion, . 




t"; 


1 


1486 


3-3 


4 43 53 


6° 46' 4" N. 


100 


Orion, . 




r\ . . . 


3 


1495 


4-0 


4 45 21 


5° 24' 56" N. 


101 


Orion, . 




r\ . . . 


8 


1514 


3-9 


4 48 31 


2° 15' 37" N. 


102 


Auriga, . 




1, ... 


3 


1520 


2-7 


4 49 50 


32° 59' 28" N. 



128 



THE NAMES AND POSITIONS OF THE MORE iMPOETANT STARS, kc— continued. 







Greek or Roman Letter ^ 


Flamsleed 






EIGHT 




1 


No. 


CONSTELLATION. 


and Synonym. 


Number. 


B.A.C. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


103 


Auriga, . 


e, . . 


7 


1540 


3-2 


h. m. 8. 

4 54 5 


43' 39' 


36" N. 


104 


Auriga, . 




^ (Sadatoni), 


8 


1541 


4-0 


4 54 48 


40' 54' 


54" N. 


105 


Auriga, . 




yj, . . . 


10 


1558 


3-3 


4 58 48 


iV 5' 


9" N. 


106 


Lepus, 




s, . . . 


2 


1575 


3-3 


5 48 


22' 31' 


9 " s. 


107 


Eridanus, 




j3 {Cur so), 


67 


1588 


2-9 


5 2 27 


5' 13' 


45" s. 


108 


Auriga, . 




a. {Capella), . 


13 


1613 


0-2 


5 8 34 


45' 53' 


6"n. 


109 


Lepus, . 




IJ,, . . . 


5 


1616 


3-3 


5 7 59 


16' 20' 


8"s. 


110 


Orion, . 




13 {Rigel), . 


19 


1623 


0-3 


5 9 15 


8° 19' 


46" s. 


111 


Orion, . 




r, ... 


20 


1638 


3-7 


5 12 16 


6' 57' 


51" s. 


112 


Taurus, . 




,8 (Ifath), . 


112 


1681 


1-9 


5 19 20 


28° 30' 


49" N. 


113 


Orion, . 




yj, . . . 


28 


1684 


3-5 


5 18 57 


2° 29' 


57" s. 


114 


Orion, . 




y (Bellatrix), 


24 


1687 


1-9 


5 19 14 


6' 14' 


59" N. 


115 


Lepus, . 




13, . . . 


9 


1715 


3-0 


5 23 32 


20° 50' 


51" s. 


116 


Orion, . 




8 (Mintaka), 


34 


1730 


2-4 


5 26 23 


0° 22' 


53" s. 


117 


COLUMBA, 




£, . . . 




1739 


3 '8 


5 27 18 


35° 3.3' 


4"s. 


118 


Lepus, . 




a, . . . 


11 


1741 


2-7 


5 27 53 


17° 54' 


7"s. 


119 


Orion, . 




X (Eeka), . 


39 


1749 


3-5 


5 29 5 


9' 51' 


32" N. 


120 


Orion, . 




1, . . . 


44 


1762 


3-0 


5 30 3 


5° 58' 


58" 8. 


121 


Orion, . 




£ (Alnilam), 


46 


1765 


1-8 


5 30 38 


1° 16' 


22" s. 


122 


Taurus, . 




I . . . 


123 


1767 


3-0 


5 31 4 


21° 4' 


31" N. 


123 


Orion, . 




ff, . . . 


48 


1780 


3-7 


5 33 13 


2° 39' 


52" s. 


124 


Dorado, , 




i8, . . . 




1791 


4-0 


5 32 40 


62° 33' 


42" s. 


125 


Orion, , 




^ (Alnitak), . 


50 


1794 


1-9 


5 35 13 


2' 0' 


6"s. 


126 


CoLUMBA, 




a {Hadar), . 




1802 


2-7 


5 35 40 


34' 8' 


0"s. 


127 


Lepus, 




7, . . . 


13 


1823 


3-8 


5 39 53 


22° 29' 


l"s. 


128 


Lepus, . 




K, ... 


14 


1840 


3-7 


5 41 59 


14° 51' 


50" s. 


129 


Orion, . 




X, . . . 


53 


1843 


2-2 


5 42 32 


9° 42' 


34" s. 


130 


Lepus, 




d, . . . 


15 


1871 


40 


5 46 35 


20° 53' 


14" s. 


131 


CoLUMBA, 




^{Wezn), . . 




1878 


2-9 


5 47 4 


35° 48' 


41" s. 


132 


Orion, . 




a {Betelgeux), 


58 


1883 


0-9 


5 49 13 


7° 23' 


9"n. 


133 


Auriga, . . 




h, • , • • 


33 


1885 


3-8 


5 50 28 


54° 16' 


33" N. 


134 


Auriga, . 




/3 (Meiikalinan), . 


34 


1895 


2-1 


5 51 27 


44° 56' 


5" N. 


135 


Auriga, . 




6, . . . 


37 


1900 


2-7 


5 52 13 


37' 12' 


15" N. 


136 


Lepus, . 




»),... 


16 


1901 


3-7 


5 51 24 


14° ir 


17" s. 


137 


Gemini, . 




V, • • • 


7 


2002 


3-5 


6 8 14 


22° 32' 


17" N. 


138 


Gemini, . 




fx, (Tejat), . 


13 


2047 


3-2 


6 16 18 


22° 34' 


9"N. 


139 


Canis Major, 




^ (Phurud), . 


1 


2051 


3 


6 16 5 


30° 0' 


54" s. 


140 


Canis Major, 




(3 {Mirzara), . 


2 


2061 


2-0 


6 17 51 


17° 54' 


7"s. 


141 


Canis Major, 




d, . . . 


3 


2066 


4-0 


6 18 4 


33° 22' 


51" s. 


142 


Gemini, . 




V, . . . 


18 


2090 


4-0 


6 22 26 


20° 16' 


50" N. 


143 


Argo, 




a (Canopus), 




2096 


0-4 


6 21 31 


52° 38' 


9"s. 


144 


Gemini, . 




y {Alhena), . 


24 


2163 


2-0 


6 31 21 


16° 29' 


33" N. 


145 


Argo, 




V, ... 




2188 


3-6 


6 34 24 


43° 5' 


58" s. 


146 


Gemini, . 




£ (Mebsuta), . 


27 


2194 


3-2 


6 37 10 


25° 14' 


21" N. 


147 


Gemini, . 




I, . . . 


31 


2206 


3-4 


6 39 7 


13° 0' 


48" N. 


148 


Canis Major, 




a (Siritos), . 


9 


2213 


-1-4 


6 40 18 


16° 33' 


58" s. 


149 


Gemini, . 




6, . . . 


34 


2237 


3-7 


6 45 32 


34° 5' 


35" N. 


150 


Canis Major, 




X, . . . 


13 


2246 


3-9 


6 45 43 


33° 22' 


54" s. 


151 


Argo, 




r, . . . 




2256 


3-3 


6 47 12 


50° 29' 


l"s. 


152 


PiCTOR, . 




a, . . . 




2260 


3-6 


6 46 58 


61° 49' 


26" s. 


153 


Canis Major, 




o\ . . . 


16 


2267 


4-0 


6 49 35 


24° 2' 


49" s. 


154 


Canis Major, 




I (Adhara), . 


21 


2293 


1-5 


6 54 18 


28° 49' 


22" s. 



129 



THE NAMES AND POSITIONS OF THE MORE IMPORTANT STARS, kc— continued. 







Greek or Roman Letter, 


Flainsteed 






RIGHT 




So. 


CONSTELLATION. 


and Syti07iijm. 


Number. 


B.A.C. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


155 


Gemini, . 


I . . . 


43 


2305 


4-0 


h. m. s. 

6 57 35 


20° 43' 51" N. 


156 


Canis Major, 




S, ... 


22 


2309 


3-5 


6 57 20 


27° 46' 38" s. 


157 


Canis Major, 




o\ . . . 


24 


2318 


3-0 


6 58 26 


23° 40' 23" s. 


158 


Canis Major, 




y, . . . 


23 


2319 


4-1 


6 58 47 


15° 28' 17" s. 


159 


Canis Major, 




b ( Wezen), . 


25 


2345 


1-8 


7 3 55 


26° 13' 8"s. 


160 


Canis Major, 






28 


2391 


3-7 


7 10 21 


26° 34' 55" s. 


161 


Gemini, . 




X, . . . 


54 


2398 


3-6 


7 11 47 


16° 44' 24" n. 


162 


Gemini, . 




5 [Wasat), . 


55 


2410 


3-7 


7 13 33 


22° 11' 3"n. 


163 


Argo, 




ff, . , . 




2414 


2-7 


7 13 15 


36° 54' 1" s. 


164 


Gemini, . 




/, ... 


GO 


2442 


4-0 


7 18 54 


28° 0' 58" N. 


165 


Canis Major, 




Yi (Aludra), . 


31 


2458 


2-4 


7 19 44 


29° 5' 20" s. 


166 


Canis jNIinor, 




^ (Gomeisa), 


3 


2462 


31 


7 21 11 


8° 30' 37" N. 


167 


Argo, 




s, . . . 


... 


2482 


3-6 


7 25 44 


43° 4' 46" s. 


168 


Gemini, . 




a {Castor), . 


66 


2485 


1-6 


7 27 35 


32° 7' 45" N. 


169 


Canis Minor, 




« {Procyon), . 


10 


2522 


0-5 


7 33 33 


5° 30' 22" N. 


170 


Argo, 






■/.,... 


... 


f 25301 
■.2531/ 


3-9 


7 34 19 


26° 32' 7" s. 


171 


Gemini, 






5«, ... 


77 


2551 


3-6 


7 37 48 


24° 39' 41" N. 


172 


Gemini, 






/3 {Pollux), . 


78 


2555 


11 


7 38 35 


28° 17' 28" N. 


173 


Argo, 






I, . . . 




2602 


3-4 


7 44 40 


24° 34' 59" s. 


174 


Argo, 






X^ • • • 


... 


2665 


3-8 


7 54 


52° 41' 15" s. 


175 


Argo, 






C, . . . 




2710 


2-6 


7 59 43 


39° 41' 36" s. 


176 


Argo, 






', ... 


15 


2728 


2-9 


8 2 52 


23° 59' 15" s. 


177 


Argo, 






7, . ., . 




2755 


3 


8 6 9 


47° 0' 46" s. 


178 


Cancer, 






/3„ . . . 


17 


2778 


3-8 


8 10 33 


9° 31' 26" N. 


179 


Ursa Major, 




0, ... 


1 


2819 


3-4 


8 21 8 


61° 5' 8" N. 


180 


MONOCEROS, 






30 


2825 


.3-9 


8 20 10 


3° 32' 46" s. 


181 


Argo, 




s, ... 


... 


2832 


2-1 


8 20 16 


59° 9' 20" s. 


182 


Argo, 




0", 


... 


2964 


3 6 


8 39 10 


32° 47' 25" s. 


183 


Hydra, . 




£t ... 


11 


2971 


3-6 


8 40 57 


6° 49' 19" N. 


184 


Argo, 




5, . . . 




2979 


2-2 


8 41 40 


54° 18' 20" s. 


185 


Hydra, . 




?. . . . 


16 


3032 


3-3 


8 49 35 


6° 21' 51" N. 


186 


Ursa Major, 




/ {Talitha), . 


9 


3048 


3-2 


8 51 40 


48° 28' 22" N. 


187 


Cancer, . 




a. {Al Hamarein), . 


65 


3055 


4-3 


8 52 28 


12° 16' 59" N. 


188 


Ursa Major, 




X, ... 


12 


3075 


3-7 


8 56 7 


47° 35' 25" N. 


189 


Argo, 




X, . . . 




3126 


2-5 


9 3 57 


42° 59' 8"s. 


190 


Lynx, 







38 


3162 


3-8 


9 12 


37° 16' 10" N. 


191 


Argo, 




A . . . 


... 


3177 


2-0 


9 11 59 


69° 15' 51" s. 


192 


Lynx, 




«, . . . 


40 


3178 


3-4 


9 14 21 


34° 51' 23" N. 


193 


Argo, 




', ... 




3186 


2-5 


9 14 9 


58° 48' 49" s. 


194 


Argo, 




", . . . 




3213 


2-8 


9 18 42 


54° 32' 27" s. 


195 


Ursa Major, 




h, . . . 


23 


3221 


3-7 


9 22 51 


63° 32' 33" N. 


196 


Hydra, . 




a {Alphard), . 


30 


3223 


2-0 


9 22 11 


8° 10' 56" s. 


197 


Ursa Major, 




6, . . . 


25 


3242 


3-2 


9 25 30 


52° 10' 41" N. 


198 


Argo, 




■^, . . . 




3257 


3-8 


9 26 22 


39° 59' 8"s. 


199 


Leo, 




0, . ... 


14 


3312 


3-8 


9 35 17 


10° 23 33" N. 


200 


Leo, 




e, ... 


17 


3331 


3-1 


9 39 36 


24° 16' 49" N. 


201 


Ursa Major, 




u, ... 


29 ■ 


3346 


4-0 


9 43 10 


59° 33' 18" N. 


202 


Argo, 




!^' • . . 


. * . 


3365 


3-4 


9 44 21 


64° 33' 33" s. 


203 


Leo, 




/M {Rasalas), . 


24 


3371 


4-1 


9 46 30 


26° 31' 28" N. 


204 


Leo, 




yj, . . . 


30 


3453 


3-6 


10 1 20 


27° 17' 58" N. 


205 


Leo, 




a (Pegulus), . 


32 


3459 


1-4 


10 2 31 


12° 30' 16" N. 



1.30 



THE NAMES AND POSITIONS OF THE MORE IMPORTANT STARS, kc— continued. 



No. 


CONSTELLATION. 


Greek or Roman Letter, 
and Synonijm. 


Flamsteed 
Number. 


B.A.C. 


MAGNITUDE. 


RIGHT 
ASCENSION. 


DECLINATION. 


206 


Hydra, . 


X, . 


41 


3473 


3-9 


h. in. s. 

10 5 14 


11° 48' 


37" s. 


207 


Ursa Major, . 


X, 




33 


3505 


3-6 


10 10 28 


43° 27' 


48" N. 


208 


Leo, 


c. 






3508 


3-6 


10 10 34 


23° 57' 


56" N. 


209 


Argo, 


u, 




... 


3516 


3-7 


10 11 7 


69° 29' 


30" s. 


210 


Leo, 


X (Abgeiba), 




41 


3523 


2-2 


10 13 54 


20° 23' 


51" N. 


211 


Ursa Major, . 


/A, 




34 


3533 


31 


10 15 47 


42° 3' 


10" N. 


212 


Hydra, . 


fi, 




42 


3568 


4-1 


10 20 46 


16° 16' 


30" s. 


213 


Leo, 


?» 




47 


3609 


4-0 


10 27 1 


9° 52' 


20" N. 


214 


Carina, . 


P, 






3619 


3-7 


10 28 6 


61° 7' 


11" s. 


215 


Argo, 


6, 






3686 


3-0 


10 39 2 


63° 59' 


7"s. 


216 


Argo, 


n, 






3695 


Var. 1 to 6 


10 40 48 


59° 6' 


23" s. 


217 


Argo, 


fi. 






3702 


30 


10 42 2 


48° 50' 


20" s. 


218 


Hydra, . 


* 






3715 


3-3 


10 44 12 


15° 37' 


8"s. 


219 


Leo Minor, . 






46 


3728 


3-9 


10 47 9 


34° 48' 


29" N. 


220" 


Crater, . 


a (Alkes), 




7 


3766 


4-1 


10 54 25 


17° 42' 


45" s. 


221 


Ursa Major, . 


/3 (Mirak), 




48 


3767 


2-6 


10 55 12 


56° 58' 


19" N. 


222 


Ursa Major, . 


« {Duhhe), 




50 


3777 


2-0 


10 56 56 


62° 20' 


41" N. 


223 


Ursa Major, . 


9, 




52 


3812 


31 


11 3 29 


45° 5' 


39" N. 


224 


Leo, 


b (Zosma), 




68 


3834 


2-8 


11 8 15 


21° 7' 


34" N. 


225 


Leo, 


6, 




70 


3838 


3-5 


11 8 28 


16° 1' 


57" N. 


226 


Ursa Major, . 


^, 




53 


3851 


3-8 


11 12 19 


32° 8' 


57" N. 


227 


Ursa Major, . 


i-, 




54 


3852 


3-8 


11 12 33 


33° 41' 


41" N. 


228 


Crater, . 


5, 




12 


3859 


3-9 


11 13 51 


14° 11' 


0"s. 


229 


Leo, 


', 




78 


3877 


4-0 


11 18 12 


11° 8' 


10" N. 


230 


Draco, . 


X (Jiiza), 




1 


3914 


4-1 


11 24 52 


69° 56' 


16" N. 


231 


Centaurus, 


X, 






3941 


3-5 


11 30 43 


62° 24' 


40" s. 


232 


Ursa Major, . 


%. 




63 


3981 


3-9 


11 40 15 


48° 23' 


22" N. 


233 


Leo, 


j3 (Denebola), 


94 


3995 


2-2 


11 43 27 


15° ir 


13" N. 


234 


Virgo, . 


(3 (Zavijava), 


5 


4002 


3-7 


11 44 58 


2° 23' 


5" N. 


235 


Ursa Major, . 


y {Phecda), . 


64 


4017 


2-6 


11 48 3 


54° 18' 


23" N. 


236 


Centaurus, 


d, . . . 




4087 


2-9 


12 2 39 


50° 6' 


34" s. 


237 


CORVUS, . 


s, . . . 


2 


4097 


3-1 


12 4 28 


22° 0' 


28" s. 


238 


Crux, . . . 


5, . . . 




4120 


3-5 


12 9 18 


58° 8' 


13" s. 


239 


Ursa Major, . 


d (Megrez), . 


69 


4123 


3-4 


12 9 59 


57° 38' 


34" N. 


240 


Corvus, . 


7. • • • 


4 


4124 


2-8 


12 10 9 


16° 55' 


51" s. 


241 


Virgo, 


v, ■ . ■ 


15 


4145 


4-0 


12 14 17 


0° 3' 


19" s. 


242 


Crux, 


a, . . . 




4187 


1-0 


12 20 29 


62° 29' 


21" s. 


243 


Corvus, . 


8 (Algorab), . 


7 


4211 


31 


12 24 11 


15° 54' 


11" s. 


244 


Crux, 


7, ■ ■ ■ 




4215 


2-0 


12 25 4 


56° 29' 


48" s. 


245 


Corvus, . 


^, . . . 


9 


4234 


2-8 


12 28 36 


22° 47' 


18" s. 


246 


Musoa, . 


a, . . . 




4245 


30 


12 30 38 


68° 31' 


44" s. 


247 


Centaurus, 


7, . . . 


• . . 


4264 


2-4 


12 35 26 


48° 21' 


20" s. 


248 


Virgo, . 


y (Porrima), 


29 


4268 


2-8 


12 36 5 


0° 50' 


44" s. 


249 


MUSCA, . 


/3, . . . 




4280 


3-5 


12 39 32 


67° 29' 


20" s. 


250 


Crux, 


/3,_ . . . 




4289 


1-6 


12 41 18 


59° 5' 


14" s. 


251 


Ursa Major, . 


s (Alioth), . 


77 


4335 


1-9 


12 49 11 


56° 33' 


23" N. 


252 


Virgo, . 


d, • •_ • 


43 


4340 


3-7 


12 50 4 


3° 59' 


43" N. 


253 


Canes Venatici, 


a [Cor. Caroli), 


12 


4346 


30 


12 50 53 


38° 54' 


55" N. 


254 


MuscA, . 


S, . . . 




4353 


3-7 


12 54 42 


70° 57' 


18" s. 


255 


Virgo, . 


I (Vindemiatrix), . 


47 


4367 


30 


12 56 42 


11° 33' 


2" N. 


256 


Hydra, . 


y, . . . 


46 


4450 


3-4 


13 12 57 


22° 15' 


24" s. 


257 


Centaudus, 


1, . . . 


... 


4458 


31 


13 14 24 


36° 7' 


54" s. 



131 



THE NAMES AND POSITIONS OF THE MOEE IMPORTANT STARS, kc— continued. 







Greek or Roman Letter, 


Flanisteed 






RIGHT 






1 


Xo. 


COXSTELLATIOX. 


and Synonym. 


Number. 


BAG. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


258 


YlRGO, . 


a (Spica), 


67 


4480 


1-2 


L. m. 3. 

13 19 24 


10° 


35' 


13" s. 


259 


Ursa Major, . 


^ (Mizar), 


79 


4484 


2-4 


13 19 30 


55° 


29' 


59" N. 


260 


Virgo, . 


I . . . 


79 


4532 


3-5 


13 29 5 


0° 


r 


59" s. 


261 


Centaurus, 


s, . . 




4549 


2-7 


13 32 55 


52° 


54' 


25" s. 


262 


Cextaurus, 


f, ... 


... 


4601 


3-8 


13 42 54 


41° 


8' 


19" s. 


263 


Cextaurus, 


//,,... 




4602 


4-5 


13 42 59 


41° 


55' 


30" s. 


264 


Ursa Major, . 


Tj (Benetnasch), 


85 


4607 


2-0 


13 43 12 


49° 


51' 


45" N. 


265 


Cextaurus, 


C, . . . 




4638 


2-8 


13 48 41 


46° 


44' 


46" s. 


266 


Bootes, . 


>! (Saak), 


8 


4648 


2-9 


13 49 27 


18° 


56' 


57" N. 


267 


Centaurus, 


13, . . . 




4669 


0-8 


13 56 4 


59° 


50' 


31" s. 


268 


Hydra, . 


w, . . . 


49 


4685 


3-5 


14 6 


26° 


9' 


4"s. 


269 


Centaurus, 


6, . . . 


5 


4686 


2-0 


14 13 


35° 


49' 


37" s. 


270 


Draco, . 


a {Thuhnn), . 


11 


4696 


3-6 


14 1 25 


64° 


54' 


6" N. 


271 


Virgo, . 


1 {Syrma), . 


99 


4727 


4-2 


14 10 15 


5° 


28' 


30" s. 


272 


Bootes, . 


a [Arctiirus), 


16 


4729 


0-1 


14 10 39 


19° 


45' 


20" N. 


273 


Bootes, . 


e, . . . 


25 


4808 


3-6 


14 27 5 


30° 


51' 


16" N. 


274 


Centaurus, 


>!,... 




4811 


2-5 


14 28 30 


41° 


40' 


26" s. 


275 


Bootes, . 


7. • • • 


27 


4812 


31 


14 27 40 


38° 


47' 


21" N. 


276 
277 


> Centaurus, 


a, . . . 


... 


f 4831 1 
I 4832 1 


0-1 


14 32 8 


60° 


22' 


43" s. 


278 


CiRCINUS, 






4835 


3-6 


14 33 37 


64° 


29' 


39" s. 


279 


Lupus, . 


c, 




4839 


2-7 


14 34 36 


46° 


54' 


55" s. 


280 


Bootes, . 


I 




30 


4849 


3-8 


14 35 54 


14° 


12' 


3"n. 


281 


Virgo, . 


IM, 




107 


4855 


3-9 


14 37 16 


5° 


10' 


47" s. 


282 


Bootes, . 


i (Izar), 




36 


4876 


2-6 


14 40 11 


27° 


32' 


17" N. 


283 


Virgo, . 






109 


4878 


3-7 


14 40 41 


2° 


21' 


26" N. 


284 


Libra, 


cc, 




9 


4895 


3-0 


14 44 48 


15° 


35' 


3"s. 


285 


Lupus, . 


13, 






4924 


■2-9 


14 51 20 


42° 


41' 


24" s. 


286 


Centaurus, 


■/., 






4928 


3-4 


14 51 59 


41° 


39' 


43" s. 


287 


Ursa Minor, . 


/3 (Kocab), 




7 


4936 


2-1 


14 51 2 


74° 


36' 


18" N. 


288 


Libra, 


7. 




20 


4950 


3-2 


14 57 38 


24° 


50' 


56" s. 


289 


Bootes, . 


(3 (JVekkar), 




42 


4958 


3-6 


14 57 48 


40° 


49' 


29" N. 


290 


Lupus, . 


I 






4987 


3-7 


15 4 22 


51° 


40' 


47" s. 


291 


Trianguluji Australe 


7. 






5005 


3-2 


15 8 38 


68° 


16' 


20" s. 


292 


Libra, 


/3, 




27 


5034 


2-7 


15 11 5 


8° 


58' 


35" s. 


293 


Bootes, . 


^ 




49 


5036 


3-5 


15 11 4 


33° 


43' 


34" N. 


294 


Lupus, . 


5, 






5046 


3-6 


15 14 8 


40° 


14' 


55" s. 


295 


Ursa IMinor, . 


7' 




13 


5094 


3-2 


15 20 55 


72° 


13' 


33" N. 


296 


Draco, . 


', 




12 


5097 


3-4 


15 22 29 


59° 


21' 


5" N. 


297 


Corona Borealis, . 


/3, 




3 


5098 


3-8 


15 23 18 


29° 


29' 


6"n. 


298 


Lupus, . 


7. 






5118 


3-3 


15 27 49 


40° 


47' 


45" s. 


299 


Serpens, . 


5, 




13 


5135 


4-0 


15 29 33 


10° 


54' 


25" N. 


300 


Corona Borealis, , 


a (Alphecca), 


5 


5143 


2-4 


15 30 2 


27° 


5' 


7"N. 


301 


Serpens, . 


a (Cor Serpentis), . 


24 


5196 


2-7 


15 38 51 


6° 


46' 


19" N. 


302 


Serpens,. 


/3, . . . 


28 


5216 


3-8 


15 41 7 


15° 


46' 


4"n. 


303 


Serpens, . 


,'-4, 






32 


5230 


3-5 


15 43 53 


3° 


5' 


33" s. 


304 


Triangulum Australe 


- /3, 








5233 


3-2 


15 45 27 


63° 


5' 


21" s. 


305 


Serpens, . 


", 






35 . 


5234 


4-2 


15 43 48 


18° 


28' 


58" N. 


306 


Serpens, . 


h 






37 


5245 


3-7 


15 45 20 


4° 


48' 


34" N. 


307 


Serpens, . 


7. 






41 


5284 


40 


15 51 22 


16° 


r 


20" N. 


308 


Ursa Minor, . 


I 






16 


5285 


4-4 


15 48 


78° 


7' 


56" N. 


309 


Scorpio, , 


•^, 






6 


5289 


31 


15 52 11 


25° 


47' 


49" s. 




132 








" ~ - 






- 


■ - 


- 





THE NAMES AND POSITIONS OF THE MORE IMPORTANT STARS, ka.— continued. 







Greek or Roman Letter, 


Flamsteed 






EIGHT 




No. 


CONSTELLATION. 


and Synonym. 


Number. 


B.A.C. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


310 


Scorpio, . 


5, . . . 


7 


5303 


2-5 


h. m. 8. 

15 53 50 


22° 18' 27" N. 


311 


Scorpio, . 


13 (Akrab), . 


8 


5329 


2-9 


15 59 2 


19' 30' 13" s. 


312 


Ophiuchus, 


d, . . . 


1 


5414 


2-8 


16 8 35 


3° 24' 37" s. 


313 


Ophiuchus, 


s, . . . 


2 


5437 


3-4 


16 12 30 


4° 25' 25" s. 


314 


Scorpio, . 


e, . . . 


20 


6447 


3-0 


16 14 30 


25° 19' 41" s. 


315 


Hercules, 


r, . . . 


22 


5463 


3-9 


16 16 26 


46° 34' 32" N. 


316 


Hercules, 


7, . . . 


20 


5466 


3-8 


16 17 4 


19° 24' 43" N. 


317 


Scorpio, . 


a (Antares), . 


21 


5498 


1-0 


16 22 40 


26° 11' 14" s. 


318 


Draco, . 


>), . . . 


14 


5512 


2-8 


16 22 30 


61° 45' 47" N. 


319 


Ophiuchus, 


X, . . . 


10 


5520 


4-0 


16 25 22 


2° 13' 32" N. 


320 


Hercules, 


^ (Korneforos), 


27 


5525 


2-8 


16 25 29 


21° 43' 50" N. 


321 


Scorpio, . 


r, , . . 


23 


5539 


2-9 


16 29 2 


27° 59' 10" s. 


322 


Ophiuchus, 


?, . . . 


13 


5548 


2-8 


16 31 6 


10° 20' 37" s. 


323 


Triangulum Australe 


, a, . . . 


• • . 


5578 ' 


2-2 


16 37 1 


68° 49' 28" s. 


324 


Hercules, 


?, . . • 


40 


5604 


30 


16 37 8 


31° 48' 10" N. 


325 


Hercules, 


'?,... 


44 


5617 


3-7 


16 39 4 


39° 7' 56" N. 


326 


Scorpio, . 


£, . . . 


26 


5632 


2-2 


16 43 3 


34° 5' 31" s. 


327 


Scorpio, . 


A . > . 


... 


5638) 
5640] 


3-3 


1 16 44 25 
I 16 44 53 


37° 51' 28" s. 


328 


Scorpio, . 


A . . . 


... 


37° 49' 44" s. 


329 


Scorpio, . 


V, • ' • 


• • • 


5661 


3-6 


16 46 50 


42° 10' 17" s. 


330 


Ara, 


?, . . . 


• • • 


5683 


3-3 


16 49 30 


55° 48' 56" s. 


331 


Ara, 


s\ . . . 


... 


5697 


4-2 


16 50 49 


52° 58' 31" s. 


332 


Ophiuchus, 


X, . . . 


27 


5708 


3-4 


16 52 28 


9° 32' 48" N. 


333 


Hercules, 


s, ... 


58 


5731 


4-0 


16 56 5 


31° 5' 23" N. 


334 


Scorpio, . 


?7, . . . 


... 


5778 


3-7 


17 4 16 


43° 5' 32" s. 


335 


Ursa Minor, . 


£, . . . 


22 


5780 


4-4 


16 57 15 


82° 13' 2"n. 


336 


Ophiuchus, 


Yj (Sdbik), 


35 


5781 


2-6 


17 4 4 


15° 35' 16" s. 


337 


Hercules, 


« (Ras Algethi), . 


64 


5821 


3-2 


17 9 38 


14° 30' 58" N. 


338 


Draco, . 


I . . . 


22 


5823 


3-3 


17 8 28 


65° 51' 0" N. 


339 


Hercules, 


5, . . . 


65 


5828 


3-3 


17 10 31 


34° 58' 9"n. 


340 


Hercules, 


■r, . . . 


67 


5834 


3-4 


17 11 13 


36° 56' 4" N, 


341 


Ara, 


7, . . . 


• • • 


5850 


3-7 


17 16 8 


56° 16' 22" s. 


342 


Ophiuchus, 


6, . . . 


42 


5851 


34 


17 15 15 


24° 53' 20" s. 


343 


Ara, 


^, . . . 


• *. 


5852 


2-9 


17 16 9 


55° 25' 29" s. 


344 


Ara, 


5, . . . 


• ■ • 


5877 


3-8 


17 21 10 


60° 35' 26" s. 


345 


Ara, 


a, . . . 


• ■ • 


5899 


30 


17 23 20 


49° 47' 16" s. 


346 


Scorpio, . 


y, . . . 


34 


5901 


2-8 


17 23 16 


37° 12' 25" s. 


347 


Scorpio, . 


>. (Shauldh), . 


35 


5915 


1-7 


17 26 8 


37° 1' 22" s. 


348 


Scorpio, . 


6, . , . 


... 


5935 


2-1 


17 29 25 


42° 55' 36" s. 


349 


Draco, . 


/S (Alwaid), . 


23 


5937 


3-0 


17 27 57 


52° 22' 59" N. 


350 


Ophiuchus, 


a {Eas-al-ague), . 


55 


5941 


2-2 


17 29 50 


12° 38' 26" N. 


351 


Serpens, . 


^, . . . 


55 


5949 


3-7 


17 31 17 


15° 19' 42" N. 


352 


Scorpio, . 


X, . . . 


• ■ • 


5970 


2-7 


17 34 52 


38° 58' 20" s. 


353 


Hercules, 


1, ... 


85 


5990 


3-9 


17 36 23 


46° 3' 55" N. 


354 


Ophiuchus, 


/3 (Celbalrai), 


69 


5996 


2-9 


17 38 2 


4° 36' 50" N. 


355 


Scorpio, . 


i\ . . . 


... 


6004 


3-4 


17 39 52 


40° 5' 0" s. 


356 


Scorpio, . 


G, . . . 


* . . 


6018 


3-5 


17 42 22 


37° 0' 26" s. 


357 


Ophiuchus, 


7. . . . 


62 


6020 


3-8 


17 42 23 


2° 44' 58" X. 


358 


Hercules, 


fi, . . , 


86 


6021 


3-5 


17 42 9 


27° 47' 8" N. 


359 


Ophiuchus, 


V, ... 


64 


6078 


3-5 


17 52 58 


9° 45' 33" s. 


360 


Draco, . 


?, . . . 


32 


6079 


3-9 


17 51 38 


53° 53' 23" N. 


361 


Hercules, 


6, . . . 


91 


6082 


4-0 


17 52 29 


37° 15' 59" N. 



133 



THE NAilES AND POSITIONS OF THE MORE IMPORTANT STARS, kc— continued. 



Ko. 


COi^STELLATION. 


Greek or Roman Letter, 
and Synonym. 


Flainsteed 

Number. 


B.A.C. 


MAGNITUDE. 


RIGHT 

ASCENSION. 


DECLINATION. 


362 


Hercules, 


b' ... 


92 


6084 


3-9 


h. m. s. 

17 53 30 


29° 15' 37" N. 


363 


Draco, . 




7 {Etanim), . 


33 


6091 


2-4 


17 54 3 


51° 30' 7" N. 


364 


Sagittarius, . 




y, . . . 


10 


6115 


3-0 


17 58 45 


30° 25' 31" s. 


3G5 


Ophiuchus, 






72 


6143 


3-8 


18 2 8 


9° 32' 64" N. 


366 


Hercules, 




0, ... 


103 


6150 


4-0 


18 3 15 


28° 44' 64" N. 


367 


Sagittarius, . 




/x, 


13 


6168 


4-0 


18 7 11 


21° 5' 13" s. 


368 


Sagittarius, 




-/;, ... 


... 


6186 


3-0 


18 10 11 


36° 47' 36" s. 


369 


Sagittarius, . 




b, . . . 


19 


6209 


2-8 


18 13 57 


29° 52' 31" s. 


370 


Serpens, . 




'/],... 


58 


6229 


3-4 


18 15 37 


2° 55' 36" s. 


371 


Sagittarius, . 




s {Kaus Australis), 


20 


6233 


2-1 


18 16 52 


34° 26' 8"s. 


372 


Telescopium, 




a, . . . 




6240 


3-6 


18 18 49 


46° r 40" s. 


373 


Sagittarius, 




X, ... 


• 22 


6263 


3-1 


18 21 11 


25° 28' 55" s. 


374 


Ursa Minor, 




d, . . . 


23 


6281 


4-3 


18 7 48 


86° 36' 41" N. 


375 


Draco, . 




%' • • • 


44 


6302 


3-7 


18 23 3 


72° 41' 10" N. 


376 


Octans, . 




ff, . . . 




5959 


5-5 


18 42 22 


89° 16' l"s. 


377 


Lyra, 




a ( Vega), 


3 


6355 


0-2 


18 33 13 


38° 40' 54" N. 


37S 


Sagittarius, 




^, . . . 


27 


6371 


3-3 


18 38 47 


27° 6' 13" s. 


379 


Lyra, 




13 (Sheliak), . 


10 


6429 


3-6 


18 46 1 


33° 14' 7"n. 


380 


Sagittarius, 




ff, ... 


34 


6440 


2-3 


18 48 27 


26° 25' 58" s. 


381 


Sagittarius, 




§) ... 


37 


6461 


3-5 


18 51 10 


21° 15' r's. 


382 


Aquila, . 




-) ... 


13 


6487 


4-1 


18 54 38 


14° 55' 9" n. 


383 


Sagittarius, 




^, . . . 


38 


6489 


2-9 


18 55 37 


30° 2' 14" s. 


384 


Lyra, 




7 {Sidaj)hat), 


14 


6491 


3-3 


18 54 50 


32° 32' 23" N. 


385 


Sagittarius, 




0, ... 


39 


6507 


3-9 


18 58 5 


21° 54' 4"s. 


386 


Sagittarius, 




' ) 


40 


6521 


3-5 


19 5 


27° 49' 50" s. 


387 


Aquila, . 




X,' 


16 


6526 


3-6 


19 25 


5° 2' 51" s. 


388 


Aquila, . 




I .... 


17 


6528 


31 


19 21 


13° 42' 2"n. 


389 


Sagittarius, 






41 


6548 


3-1 


19 3 13 


21° 11' 52" s. 


390 


Sagittarius, 




/S'\ . '. . 




6608 


3-9 


19 14 44 


44° 39' 51" s. 


391 


Sagittarius, 




,r-, . . . 




6610 


4-4 


19 15 16 


45° 0' 21" s. 


392 


Draco, . 




6 {Taiis), 


57 


6612 


3-2 


19 12 32 


67° 28' 4"n. 


393 


Sagittarius, 




a, . . . 




6622 


4-0 


19 16 16 


40° 49' 18" s. 


394 


Sagittarius, 




s, ■ ■ ■ 


44 


6619 


3-9 


19 15 18 


18° 3' 9" s. 


395 


Cygnus, . 




■A, . . . 


1 


6623 


3-9 


19 14 34 


53° 9' 53" N. 


396 


Aquila, . 




8, . . . 


30 


6646 


3-5 


19 19 57 


2° 53' 46" N. 


397 


Cygnus, . 




13 (Abbireo), . 


6 


6690 


3-0 


19 26 17 


37° 43' 47" N. 


398 


Cygnus, . 




1, ... 


10 


6697 


3-9 


19 26 56 


51° 29' 43" N. 


399 


Sagitta, . 




a, . . . 


5 


6739 


4-3 


19 35 11 


17° 45' 45" N. 


400 


Aquila, . 




7 (I'arazed), . 


50 


6772 


2-8 


19 41 2 


10° 20' 44" N. 


401 


Cygnus, . 




d, . . . 


18 


6779 


3-0 


19 41 32 


44° 51' 42" N. 


402 


Sagitta, . 




d, .. . 


7 


6783 


3-7 


19 42 30 


18° 15' 51" N. 


403 


Aquila, . 




a (Ahair), . 


53 


6802 


10 


19 45 25 


8° 34' 42" N. 


404 


Aquila, . 




r„ ... 


55 


6811 


3-9 


19 46 52 


0° 43' 24" N. 


405 


Aquila, . 




/3 (Ahhain), . 


60 


6833 


40 


19 49 55 


6° 7' 56" N. 


406 


Draco, . 




£, ... 


63 


6836 


3-9 


19 48 32 


69° 59' 15" N. 


407 


Pavo, 




6, ... 




6873 


3-6 


19 57 54 


66° 27' 30" s. 


408 


Sagitta, . 




7, . . . 


12 


6858 


3-6 


19 53 52 


19° 11' 42" N. 


409 


Aquila, . 




d, . . . 


6.5 


6934 


3-4 


20 5 38 


1° 8' 50" s. 


410 


Cygnus, . 




. . . 


31 


6965 


3-8 


20 10 10 


46° 24' 32" N. 


411 


Capricornus, 




rj} USud-adh- ) 
a" J dhahih), ) 


5 


6972 


4-5 


20 11 33 


12° 50' 50" s. 


412 


Capricornus, 




6 


6974 


3-8 


20 11 57 


12° 53' 7" s. 


413 


Capricornus, 




/3, . . . 


9 


6995 


3-4 


20 14 50 


15° 7' 40" s. 




134 

















4 



THE NAMES AND POSITIONS OF THE MORE IMPORTANT STARS, kc— continued. 







Greek or Roman Letter^ 


Flamsteed 






RIGHT 




1 
1 


No. 


CONSTELLATION. 


and Synonym. 


Number. 


B.A.C. 


MAGNITUDE. 


ASCENSION. 


DECLINATION. 


414 


Pavo, 


a, . . . 




7004 


21 


b. 111. s. 

20 16 5G 


57' 5' 


11" s. 


415 


Cygnus, . 


7. . . . 


37 


7022 


2-3 


20 18 17 


39° 54' 


18" N. 


416 


Delphinus, 


£, . . . 


2 


7088 


4-0 


20 27 57 


10° 55' 


47" N. 


417 


Indus, 


a, . . . 




7096 


3-2 


20 29 50 


47° 40' 


29" s. 


418 


Delphinus, 


/3 (Eotaner), . 


6 


7121 


3-7 


20 32 23 


14° 12' 


49" N. 


419 


Pavo, 


/3, . _ . . 




7129 


3-4 


20 35 3 


66° 35' 


52" s. 


420 


Delphinus, 


a (Svalocin), 


9 


7149 


3-9 


20 34 32 


15° 31' 


28" N. 


421 


Cygnus, . 


« (Arided), . 


50 


7171 


1-5 


20 37 41 


44° 53' 


15" xv. 


422 


Aquarius, 


e, . . . 


2 


7196 


3-8 


20 41 43 


9° 53' 


52" s. 


423 


Delphinus, 


7. 




12 


7200 


4-0 


20 41 33 


15° 43' 


46" N. 


424 


Cygnus, . 


s, 




53 


7204 


2-7 


20 41 46 


33° 33' 


31" N. 


425 


Cepheus, 


V, 




3 


7220 


3-6 


20 43 3 


61° 24' 


43" N. 


426 


Indus, . 


/S, 






7228 


3-8 


20 46 13 


58° 52' 


6"s. 


427 


Cygnus, . 


f, 




58 


7277 


4-0 


20 53 4 


40° 44' 


40" N. 


428 


Cygnus, . 


1, 




62 


7333 


3-7 


21 55 


43° 29' 


28" N. 


429 


Cygnus, . 


?, 




64 


7368 


3-5 


21 8 15 


29° 46' 


33" N. 


430 


Cepheus, 


a {Alder amin), 


5 


7416 


2-6 


21 15 57 


62° 7' 


10" N. 


431 


Capricornus, . 


I . . . 


34 


7445 


3-8 


21 20 23 


22° 53' 


12" s. 


432 


Aquarius, 


(3 {Sadalsuud), 


22 


7478 


3-1 


21 25 46 


6° 3' 


17" s. 


433 


Cepheus, 


(S (Alpirk), . 


8 


7493 


3-4 


21 27 14 


70° 4' 


39" N. 


434 


Capricornus, . 


y {Deneb Algedi), . 


40 


7525 


3-8 


21 34 


27° 9' 


29" s. 


435 


Pegasus, . 


£ {Enif), . . 


8 


7561 


2-4 


21 38 47 


9° 22' 


1 5" N. 


436 


Capricornus, . 


d, . . . 


49 


7580 


30 


21 40 58 


26° 37' 


30" s. 


437 


Grus, 


7, ■ ■ ■ 




7613 


31 


21 47 16 


37° 52' 


54" s. 


438 


Aquarius, 


a [Sadalmelik), 


34 


7688 


3-2 


22 8 


0° 51' 


14" s. 


439 


Grus, . . . 


a, . . . 




7692 


1-8 


22 1 18 


47° 29' 


36" s. 


440 


Pegasus, . 


1, . . . 


24 


7706 


4-0 


22 1 53 


24° 48' 


31" N. 


441 


Pegasus, . 


&, . . . 


26 


7723 


3-8 


22 11 2 


8° 19' 


51" s. 


442 


Cepheus, 


Z, . . . 


21 


7749 


3-5 


22 7 2 


57° 39' 


32" N. 


443 


Toucan, . 


a, . . . 




7767 


2-9 


22 10 58 


60° 48' 


27" s. 


444 


Aquarius, 


7 (Sadachbia), 


48 


7795 


4-0 


22 15 58 


1° 56' 


28" s. 


445 


Aquarius, 


I . . . 


55 


7832 


3-8 


22 23 10 


0° 34' 


56" s. 


446 


Piscis Australis, . 


13, . . . 


17 


7842 


4-3 


22 25 15 


32° 54' 


36" s. 


447 


Lacerta, 




7 


7855 


3-9 


22 26 46 


49° 42' 


59" N. 


448 


Aquarius, 


V, . . . 


62 


7868 


4-2 


22 29 42 


0° 41' 


3"s. 


449 


Piscis Australis, . 


£, . . . 


18 


7898 


4-0 


22' 34 34 


27° 43' 


15" s. 


450 


Grus, 


13, . . . 




7904 


2-2 


22 36 5 


47° 27' 


33" s. 


451 


Pegasus, . 


^ (Homan), . 


42 


7908 


3-6 


22 35 58 


10° 15' 


26" N. 


452 


Pegasus, . 


V, ■ ■ ■ 


44 


7923 


31 


22 37 51 


29° 38' 


47" N. 


453 


Grus, 


£, . . . 


. . . 


7946 


3-6 


22 41 54 


51° 53' 


42" s. 


454 


Pegasus, . 


/X,, . . . 


48 


795S 


3-7 


22 44 42 


24° r 


18" N. 


455 


Cepheus, 


/, . . . 


32 


7967 


3-6 


22 45 46 


65° 37' 


20" N. 


456 


Aquarius, 


X, . . . 


73 


7970 


3-8 


22 46 52 


8° 9' 


53" s. 


457 


Aquarius, 


d, . . . 


76 


7980 


3-4 


22 48 49 


16° 21' 


17" s. 


458 


Piscis Australis, . 


a (Fomalhaut), 


24 


7992 


1-3 


22 51 34 


30° 12' 


19" s. 


459 


Andromeda, . 


0, ... 


1 


8023 


3-8 


22 56 52 


41° 44' 


10" N. 


460 


Pegasus, . 


(3 (Scheat), . 


53 


8032 


2-6 


22 58 26 


27° 29' 


13" N. 


461 


Pegasus, . 


a [lilarkab), . 


54 


8034 


2-6 


22 59 17 


14° 36' 


49" N. 


462 


Aquarius, 


C-, 


88 


8062 


3-6 


23 3 35 


21° 46' 


10" s. 


463 


Pisces, . 


7> ■ ■ ■ 


6 


8105 


3-8 


23 11 28 


2° 40' 


52" N. 


464 


Cepheus, 


y (Alrai), 


35 


8238 


3-4 


23 34 50 


77° r 


■ 6" N. 



135 



INDEX TO CHART OF THE MOON. 



Lunar Mountains. 



Alps 

Altai Mountains 


Cd 
Ba 


Apennines 

Carpatliian Mts.... 
Caucasus 


Cc 
Cc 
Bd 


Corderillas 


Db 


D'Alembert Mts. 


Db 


Doerfel Mountains 


Ca 



Henaus Mountains Be 

Hercynien Mts. ... Do 

Leibnitz Mts. ... Ba 

Mont Blanc ... Bd 

Pyrenees Ab 

Riphees Mts. ... Cb 

Rook Mountains Db 

Taurus Mts. ... Ad 



Lunar Seas, Gulfs, &c. 



Bay of Dews ... Dd 
Bay of Rainbows Cd 
GreatAlpine Valley Bd 



Gulf of Fire ., 
Hunaboldt's Sea. 
Lake of Death . 
,, Sleep ., 
Mare Austral e . 



Cc 
Ad 
Bd 
Bd 
Aa 



Marsh of Sleep ... Ac 

Middle Gulf ... Cc 

Ocean of Tempests Dc 

Sea of Clouds ... Cb 

„ Cold ... Cd 

„ Corruption Cc 

„ Crisis ... Ac 

„ Fecundity Ab 



Sea of Liquids .., 

„ Nectar ... 

„ Serenity... 

„ Showers... 

„ Tranquil- 
lity ... 

„ Vapours... 
Smyth Sea 



Db 
Ab 
Be 

Cd 

Ac 
Be 
Ab 



Lunar Craters. 



Abenezra 

Abulfeda 
Agrippa 

Airy 

Aids 

Alhazen 
Albategnius . . . 
Aliacensis ... 
Almanon 
Alpetragius ... 
Alphonsus . . . 
Anaxagoras ... 
Anaximauder 
Anaximenes... 
Apianus 
AppoUonius... 

Arago 

Archimedes ... 

Archytas 

Aristarchus ... 

Aristillus 

Aristoteles ... 

Arnold 

Arzachel 

Atlas 

Autolycus ... 

Bacon 

Barocius 
Barrow 

Bayer 

Belli nus 
Berzelius 
Bessarion 

Bessel 

Biachini 

Billy 

Biot 

Blancanus ... 

Bonito 

Bonpland 
Bouguer 

Briggs 

Bullialdus ... 
Burckhardt ... 

Buch 

Burg 

Callppus 
Campanus . . . 

Capella 

Capuunus 
Cardanus 
Casatus 

136 



Bb 
Ba 
Be 
Bb 
Bd 
Ac 
Ba 
Ba 
Ba 
Cb 
Cb 
Cd 
Cd 
Cd 
Bb 
Ac 
Be 
Cd 
Bd 
Dc 
Bd 
Bd 
Bd 
Cb 
Bd 
Bd 

Ba 
Ba 
Bd 
Ca 
Ca 
Ad 
De 
Be 
Cd 
Db 
Ab 
Ca 
Cd 
Cb 
Cd 
Dc 
Cb 
Ad 
Ba 
Bd 

Bd 
Cb 
Ab 
Ca 
De 
Ca 



Cassini 

Cathcarina ... 
Cavalerius ... 
Cavendish ... 
Cepheus 

Certius 

Chacornae ... 
Chevalier 

Clavius 

Cleoraedes ... 
Cleostratus ... 
Colombo 
Condurcet ... 

Cook 

Copernicus ... 

Cruger 

Cuvier 

Cyrillies 

Damoiseau . . . , 

Daniell 

Davy 

Delambre 
De la Rue ... 
Delaunay 

Delisle 

Delue 

Descartes 
Diophantes ... 

Donati 

Doppelmayer 

Encke 

Endymion ... 
Eratosthenes 
Euclides 
Eudoxus 
Euler 

Fabricus 

Fay 8 

Fermat 

Femelius 
Firminicus ... 
Flammarion... 
Flamsteed ... 
Fontana 
Fontenelle ... 

Fourier 

Fracastorius... 
Franklin 
Fraunhofer ... 

Gambart 



Bd 
Bb 
De 
Db 
Ad 
Ba 
Be 
Ad 
Ca 
Ac 
Cd 
Ab 
Ac 
Ab 
Cc 
Db 
Ba 
Bb 

Db 
Bd 
Cb 
Bb 
Bd 
Bb 
Cd 
Ba 
Bb 
Dc 
Bb 
Db 

De 
Bd 
Cc 
Cb 
Bd 
Cc 

Ba 
Bb 
Bb 
Ba 
Ac 
Cb 
Db 
Db 
Cd 
Da 
Ab 
Ad 
Aa 

Ce 



Gartner 
Gassendi 
Gaurieus 
Gauss ... 
Geber ... 
Gemma Frisius 
Geminus 
Gerard ... 
Godin ... 
Goldsmidt 
Grimaldi 
Gruemberger 
Guttemberg . 



Hagecius 

Hainzel... 

Halley ... 

Hansen... 

Hansteen 

Harding 

Helicon 

Hell ... 

Hercules 

Herodotus 

Hermann 

Herschel 

Herschel 

Hesoidus 

Hevel . . . 

Hevelius 

Hind ... 

Hipparehus 

Horrocks 

Hortensius 

Hypatia 

Inghirami 

Jacobi ... 
Jansen ... 
Julius Caesar 

Kane 

Kepler ... 
Kicestner 
Kinau ... 
Kirch . . . 
Kirminicus 
Klapreth 
Kraft ... 
Krustern 



Bd 
Db 
Ca 
Ad 
Bb 
Ba 
Ad 
Dd 
Be 
Cd 
Db 
Ca 
Ab 



. Ba 

.. Ca 
. Bb 
. Ca 
. Db 
. Dd 
. Cd 
. Ca 
. Bd 
. Dc 
. Db 
. Cb 
. Cd 
. Cb 
. Dc 
. Dc 
. Bb 
. Bb 
. Bb 
. Cc 
. Bb 

. Da 

,. Ba 

,. Be 

Be 

Bd 
Dc 
Ab 
Ba 
Cd 
Ac 
Ba 
Dc 
Bb 



Lacaille Cb 

La Condamine Cb 



Lagrange 

Lagut ... 

Lalande 

Lambert 

Landsberg 

Langrenus 

Lapeyrouse 

Laplace... 

Laxell ... 

Legendre 

Lemonnier 

Leronne 

Leverier 

Licetus ... 

Liebeg ... 

Lilius ... 

Lindenau 

Linne ... 

Lockyer 

Lohrmann 



Da 
Ba 
Cb 
Ce 
Cb 
Ab 
Ab 
Cd 
Ca 
Ab 
Be 
Db 
Cd 
Ba 
Db 
Ba 
Ba 
Be 
Ba 
Db 



Longomontanus Ca 



Macrobrius 

Madler ... 

Maginus 

Manilius 

Manzinus 

Maraldi 

Marius ... 

Marnus... 

Maskelyne 

Maurotychui 

Mayer ... 

Menelaus 

Mercator 

Mersenius 

Messala... 

Messier... 

Metius ... 

Milichius 

Moretus 

Mosting 

Mutus ... 

Nasmyth 

Newton... 
Neander 
Newton 
Nicollet 
Nieolai ... 
Nonus ... 

Oken 
Olbers ... 



Ac 
Bb 
Ca 
Be 
Ba 
Ae 
Dc 
Aa 
Be 
Ab 
Ce 
Be 
Cb 
Db 
Ad 
Ab 
Aa 
De 
Ca 
Cb 
Ba 

Ca 
Ca 
Aa 
Ca 
Cb 
Ba 



Aa 
Dc 



Otto Struve . . 

Palmieri 

Parrot 

Parry 

Peirce 

Pentland 
Petarius 

Peters 

Phillips 
Philolaiis 
Phocylides .. 

Piazzi 

Picard 

Piceolomini . . 

Pietet 

Pitatus 

Pitiseus 

Plana 

Plato 

Playfair 

Plinius 

Plutarehus .. 

Poisson 

Polybius 
Pontanus 
Posidonius . . 

Proclus 

Ptolemaus .. 
Purbaeh 
Pythagoras ,. 

Ramsden 
Reaumer 
Reiehenbach 

Reiner 

Reinhold 

Rheita 

Rieeioli 

Riecius 

Ritter 

Roeca 

Roemer 

Ross , 

Rost , 

Sabine 

Sacrobosco .. 
Santbech 
Sasserides .., 
Saussure 
Scheiner 
Schickhard .. 
Schiller , 



De 

Db 
Bb 
Cb 
Ac 
Ba 
Ab 
Bd 
Ab 
Cd 
Da 
Da 
Ae 
Bb 
Ca 
Ca 
Ba 
Bd 
Cd 
Bb 
Be 
Ae 
Ba 
Bb 
Bb 
Cd 
Ae 
Cb 
Cb 
Cd 

Ca 
Bb 
Aa 
De 
Cc 
Aa 
Db 
Ba 
Be 
Db 
Ac 
Be 
Ca 

Be 
Bb 
Ab 
Ca 
Ca 
Ca 
Da 
Ca 



Schmidt 
Schomberg ... 
Schroter 
Schubert 
Scoresby 

Seechi 

Segner 

Seleucus 

Seneca 

Sharp 

Short 

Simpelius ... 

Sirsadis 

Smythi 

Snellius 
Sosigenes 
Stevinus 
Stiborius 

Stofler 

Street 

Tacittis 

Thales 

Thebit 

Theophilus ... 
Timoeharis ... 

Tralles 

Triesnecker ... 
Trouvelot ... 
Turnerius ... 
Turuntius ... 
Tycho 

Vasco di Gama 
Vendelinus ... 

Vieta 

Vitello 

Vitruvius ... 
Vlacq 

Walter 

Wargentin . . . 
Warzelbauer 

Webb 

Werner 

WilhelmL ... 

Wilson 

Wolf 

Xenopbanes ... 



Be 
Ba 
Cc 
Ac 
Bd 
Ac 
Ca 
Dc 
Ac 
Cd 
Ca 
Ba 
Db 
Ac 
Ab 
Be 
Aa 
Ba 
Ba 
Ca 

Bb 
Bd 
Cb 
Bb 
Cc 
Ac 
Be 
Db 
Aa 
Ac 
Ca 

Dc 
Ab 
Db 
Da 
Be 
Ba 

Ca 
Da 
Ca 
Ab 
Bb 
Ca 
Ca 
Cc 

Dd 



Zach Ba 

Zupus Db 



CHART OP THE MOON. 



/'. hi,?-' 








>x _^ 



<<-\ 


























O^^o^C 



.r 



II. 5 






A/, 









V Ir' > /."U*^ 



o> 









»j/ ii\ 
& 



r 



V-i, \ 



■^ 



\i9- 










.^ '^V^ 



\ 























t'- '^'T^fe^^^':''^^ 



NORTH 



O Co// A /119AS, frfcnburyk. 



■■^'^.-^a^ 






* V 



^ape tor tbc Mortbern Ibemispbere. 

No. 1 No. 2 




CAN, • • > / 

V ^ *W 



Each of the above Circular Maps is a true representation of the configurations of the principal Stars at the dates and hours given in 
Table 5 on pages 122 and 123. 

The centre of the Map is the point overhead, or the zenith of the observer ; while the horizon, containing the principal compass 
points, is indicated by the circular line near the circumference. The horizon of Britain (in the !Maps Hor. of Brit.) includes the horizon 
for Central Europe and Canada ; and the horizon of the United States (in the IMaps Hor. of U.S.) the horizon for Southern Europe. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Charts, each number indicating the 
position in the sky, of the centre of its corresponding Chart. 

137 



flbaps tor tbe mortbern IDemiepbere. 



No. 5 



No. 7 



No. 6 




No. 8 




Each of the above Circular Maps is a true representation of the configurations of the principal Stars at the dates ami hours given in 
Table 5 on pages 122 and 1 23. 

The centre of the Map is the point overhead, or the zenith of the observer ; while the horizon, containing the principal compass 
points, is indicated by the circular line near the circumference. The horizon of Britain (in the IMaps //o?-. of Brit.) includes the horizon 
for Central Europe and Canada ; and the horizon of the United States (in the Maps Hor. of U.S.) the horizon for Southern Europe. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Charts, each number indicating the 
position in the sky, of the centre of its corresponding Chart. 

139 



/Iftape for tbe H^ortbern IDemispbcre. 

No. 9 No. 10 





No. 11 



No. 12 




Each of the above Circular Maps is a true representation of the configurations of the principal Stars at tlic dates and houi-s given in 
Table 5 on pages 122 and 123. 

The centre of the Map is the point overhead, or the zenith of the observer ; while the horizon, containing the principal compass 
points, is indicated by the circular line near the circumference. The horizon of Britain (in the Maps Hor. of Brit.) includes the horizon 
for Central Europe and Canada ; and the horizon of the United States (in the Maps Hor. of U.S.) the horizon for Southern Europe. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Charts, each number indicating the 
position in the sky, of the centre of its corresponding Chart. 

T 141 



flftaps for tbe Soutbern Ibemispbere. 



No. 13 



No. 15 



No. 14 




No. 16 




Each of the above Circular Maps is a true representation of the configurations of the principal Stars at the dates and hours .-iven in 
Table 6 on pages 124 and 125. ° 

_ The centre of the Map is the point overhead, or the zenith of the observer j while the Jiorizon, containing the principal compass 
points, IS indicated by the circular line near the circumference. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Charts, each niunber indicating the 
position m the sky, of the centre of its corresponding Chart. 

143 



flfcaps tor tbe Soutbern 1Demiepbere< 



No. 17 



No. 18 




No. 19 



No. 20 




Each of the above Circular Maps is a true representation of the configurations of the principal Stars at the dates and hours given in 
Table 6 on pages 124 and 125. 

The centre of the Map is the point overhead, or the zenith of the observer ; while the horizon, containing the principal compass 
points, is indicated by the circular line near the circumference. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Cliarts, each number indicating tlie 
position in the sky, of the centre of its corresponding Chart. 

145 



flftaps tor tbe Soutbern Demiepbere 



No. 21 



No. 22 




No. 23 



No. 24 




Each of the above Circular Maps is a true representation of the configurations of the principal Stars at the dates and hours given in 
Table 6 on pages 124 and 125. 

The centre of the Map is the point overhead, or the zenith of the observer ; while the horizon, containing the principal compass 
points, is indicated by the circular line near the circumference. 

The large numbers inside the Maps are for facilitating the use of the twelve square Star Charts, each number indicating tlio 
position in the sky, of the centre of its corresponding Chart. 



Inteeesting Objects foe the Telescope. 



Chart 1. 

Interesting Objects foe the Telescope. 



DOUBLE STABS. 

52 

2 (Hcv.) 

4 {Hev.) 

1 

2 



Camelopardalis. 



19 (Rev.) 
32 (Hev.) 



6th and 7th magnitudes ; distance only 0"'5 — a difficult object even for large telescopes. 

Magnitudes 5 and 9 ; distance 2""5. 

Magnitudes 5 and 9 ; distance 15". 

Magnitudes 6 and 6 ; distance 10". An interesting object. 

This 6th magnitude yellowish star has a bluish 7th magnitude companion, distant 2". 

A 5th magnitude star with two faint companions, distant 25" and 1". 

A 5th magnitude star with faint companion, distant 20". 

Magnitudes 5'5 and 6"5 ; distance 22". 



NEBULA AND STAB CLUSTEBS. 

940 A foirly large and conspicuous cluster, with slight condensation towards the centre. 



1541 
1691 



Large and elongated nebula, with increase of brilliancy at centre. 
Bright and large nebula, with slight condensation near centre. 



DOUBLE STABS 



a 
a 

V 

t 
\ 

48 



Cassiopeia. 

This greenish coloured 5th magnitude star has a deep blue 7th magnitude companion, distant 3". 

A reddish star, with a 9th magnitude companion distant 60". 

A binarj' star discovered by Herschel ; magnitudes 4 and 7 ; distance 6" ; period 222 years. 

This 4th magnitude star appears in a small telescope to have only a single companionj at a distance of 30". 

The companion, however, is itself double ; distance 3". 
Also a triple star. Magnitudes 4, 7, and 9 ; distances 1"'5 and 8". 
A very close double star ; distance only 0"'5. 
Magnitudes 5 and 8, distance 1". 



NEBULA AND STAB CLUSTEBS. 



M. 52 

382 

M. 103 

63 

120 

£56 

392 

5031 



An irregular star cluster. 

A cluster well seen with a very small telescope. 

Star cluster ; a most beautiful object. 

A coarse and widely scattered cluster of nearly circular shape, with a diameter of about 20'. 

A very fine cluster, shaped somewhat like the letter W. 

Large and rich cluster, of 7 to 10 magnitude stars. 

A ricli cluster, 15' in diameter ; a beautiful object. 

A large faint cluster of minute stars, discovered by Miss Herschel. 



VABIABLE STABS. 

a Discovered by Birt in 1831 to be variable from 2-2 to 2-8 magnitude, in an irregular period. 
E This deep red-coloured star was discovered by Pogson, in 1853, to be variable in a period of about 426 
days. Maximum magnitude, 4-8 to 6-8 ; minimum 12. 
A red star, whose variability was discovered by Kiirgur in 1870. Maximum magnitude, 6-5 to 7 ; minimum 

11 ; period 436 days. 
Discovered by Argelander to be variable in 1861. Maximum magnitude, 6-7 to 8 ; minimum 13 ; period 615 days. 
^, 73", 40, and 55, are suspected of variability. 

DOUBLE STABS / C E P H E U S. 

Magnitudes 4, 5, and 8 ; distance 7" ; colours, pale yellow and blue. 

Magnitudes 3 and 8 ; distance 14". 

A sixth magnitude multiple star. 

A yellowish 4'5 magnitude star, with a 7th magnitude blue companion, distant 5". 

A very fine double star ; colours, yellow and blue ; distance 40". 

A binary star. Discovered at Pulkowa to be triple ; magnitudes, 5, 9, and 11. 

A binary star. Magnitudes 5-5 and 8 ; distance 27" ; colours — bright yellow and blue. 

STAB CLUSTEB. 

4590 I A very rich cluster, discovered by Herschel. 

150 {Description of Chart 1 continued over the next page.) 



K 

15 

8 

TT 
O 



CHART 1. 




Construated hy\ R 



W. Peck EdinJ 



VARIABLE STABS. C E P H E U S—conti7iued. 

K Discovered by Pogson, in 1856, to be variable from magnitudes 5 to 10, in an irregular period. 
Variable from magnitudes 4 to 5 ; discovered by Hind in 1848. 
A very regular variable star ; period 5*4 days ; maximum 3'7 ; minimum 4'9. 
Suspected of variability. 



Draco. 



DOUBLE STARS. 

A 3rd magnitude star, with a faint companion, distant about 5". 

These stars appear to the unaided eye as a single object. When viewed with a small telescope, however, three 

stars are seen ; distances 90" and 4". 
Magnitudes 4'5 and 5 ; distance 3". Thought to be a binary star. 
Magnitudes 5 and 5 ; distance 62" ; colour, pale grey. 
Noticed by Flamsteed to be double ; magnitudes 4'5 and 5 ; distance 30". 

These yellow-coloured stars, of the 5th and 6th magnitude respectively, are distant from each other 20". 
A 5th magnitude triple star ; distances 3" and 89" ; colours — white, light blue, and red. 
A 5th magnitude star, with a companion, distant 147". 
A 4th magnitude star, with a companion, distant 30". 
Magnitudes 4"5 and 7 ; distance 30". 
Magnitudes 4 and 7 ; distance 3". Thought to be a binary star. 



V 
16 and 17 



V 

40 and 41 

39 

46 

47 

o 

6 



NEBULA AND STAR CLUSTERS. 



4373 

4415 
4517 



A planetary nebula, with a diameter of over 30". Can be well seen with a telescope of four inches aperture. 
A fairly large and brilliant nebula, whose light has been suspected to be variable. 
A large but not very dense cluster of 7th magnitude and fainter stars. 



VARIABLE STARS. 

<}} and /J> are thought to be variable. 



DOUBLE STARS. 



Ursa Major. 

{The remaining part of this Constellation is given on Chart It.) 



G" 

T 

16 
23 

V 

41 

a 

65 

K 

NEBULA. 

M. 81 & M. 82 

M. 97 

VARIABLE STARS. 



A 5th magnitude star, with an 8th magnitude companion, distant 3". 

A wide double star ; distance 55". 

Also a wide double star ; distance 59". 

Magnitudes 4 and 9 ; distance 23". 

A 4th magnitude star, with companion, distant 11". 

Magnitudes 6 and 8 ; distance 82". 

This bright star has an 8th magnitude companion, distant 380". 

Triple star ; magnitudes 6 '4, 7, and 8 ; distances 64" and 4". 

One of the finest objects in the heavens, when viewed with a small telescope. 

Two fairly bright nebulsB, about half a degree apart. 

A large and faint planetary nebula, much larger than the apparent size of Jupiter. 



E 



/3 



A remarkable variable star, discovered by Pogson in 1853. The brilliancy at maximum varies from magoiitudes 
6 to 8 ; but at minimum it is only about 12. These variations are performed in a period of about 303| days. 

The magnitude of this star is also subject to a great range of variation. The maximum is very ii'regular, 
varying from 65 to 8 ; the minimum is often as low as the 13tli magnitude. 

Suspected of variability with a period of 35 days. 



a, ifr, rVj S^ 6, f, and Tjj are also thought to be slightly variable. 



DOUBLE STARS. 



Ursa Minor. 

The light of the bright star is yellowish, the faint companion 



{Polaris) Magnitudes 2 and 9 ; distance 19", 

being of a bluish colour. 
Magnitudes 5 and 8 ; distance 56". 
A 2nd magnitude star with a companion, distant 200". 
A star of the 4th magnitude, with companion, distant 78". 

A yellowish 6th magnitude star, with a 7tli magnitude companion of the same colour, distant 30". 
VARIABLE STARS. 

^ j Thought by Struve to be subject to a slight variation of magnitude in a long period. 
4 1 Thought to be variable. 

161 



Chart 2. 

Interesting Objects for the Telescope. 



■*** 



Andromeda. 

DOUBLE STABS. 

Magnitudes 4 and 11 ; distance 49". A difficult object. 

One of the finest objects in the heavens. The large star is of a golden colour, and the 6th magnitude com- 
panion is blue. The distance between these stars is 10". In 1842 the small star was discovered by 
Struve to be double ; distance less than 1". 

Magnitudes 4 and 9 ; distance 36". 

A binary star. Magniti^des 5'5 and 7 ; distance 1""5 ; period 349 years. 

A 6th magnitude star, with a 7th magnitude companion at a distance of 16". 



TT 

36 

59 



NEBULA AND STAR CLUSTERS. 
M. 31 



M. 32 

457 
527 



The Great Nebula, sometimes called the Queen of Nebulse. A most 
telescopes, and easily seen with the unaided eye on a moonless night, 
gaps can be seen, and also hundreds of small stars. 

A faint star cluster, in same low power field as large nebula. 

A cluster of coarsely scattered stars, about one and a-half degrees in diameter. 

Nebula 15' long by 3' broad ; discovered by Miss Herschel. 



interesting object, even for small 
With large instruments, long, dark 



VARIABLE STARS. 

R I A long-period variable star of a rich orange colour ; discovered by Argelander in 1858. Maximum m^nitude, 
I 5'6 to 8-6 ; minimum 13 ; period 405 days. 

i, 28, 36, ^, and 49 thought to be slightly variable. 



DOUBLE STARS. 



Aries. 



X 

10 
14 
30 
33 

TT 

41 

€ 

52 



A very fine object for small telescopes. It is probably the first double star that was discovered. 

components are nearly equal in magnitude, and are separated from each other by 9". 
Magnitudes 5 and 8 ; distance 37". Also a good object for small instruments. 

A close binary star- of the 6th magnitude. The companion is of the 8th magnitude, at the distance of 1"'5. 
A triple star. Magnitudes 6, 9, and 10 ; distances 83" and 106". 
A beautiful double star. Magnitudes 6 and 6'5 ; distance 39". 
A 6th magnitude star, with a 9th magnitude companion, distant 29". 
A triple star. Magnitudes 5, 8, and 11 ; distances 3" and 25". 
A 4th magnitude star, with a faint companion at a distance of 20". 
A close double star. Magnitudes 5 and 6 ; distance only l"-5. 
A quadruple star of the 6th magnitude, but seen only with a powerful telescope. 



The 



VARIABLE STARS. 

3, 7, 19, and e | Thought to be variable. 



DOUBLE STARS. 



Pegasus. 



1 

3 

e 

K 

20 
30 
33 



A 4th magnitude star, with a 9th magnitude companion, distant 36". 

A 6th magnitude star, with a 7'5 magnitude companion at a distance of 39". 

This 2nd magnitude star has two companions ; magnitudes 8 and 13 ; distances 85" and 138". 

Magnitudes 4 and 11 ; distance 11". The primary is itself a very close double star. 

Magnitudes 6 and 13 ; distance 51". An e.xceedingly difficult object. 

A 5th magnitude star, with a faint companion, distant 6". 

A triple star. Magnitudes 6, 7-5, and 9 ; distances 2"-5 and 64". 

152 [Description of Chart 2 continued over the next page.) 



Chart 2. 




P E G A S U ^—continued. 



DOUBLE STARS— continued. 



V 

85 



A 3rd magnitude star, witli 11th magnitude companion, distant 90". 

Magnitudes 4 and 11 ; distance 12". 

A 2nd magnitude star, with faint comparion, distant 98". 

Magnitudes 6 and 9 ; distance 15". The large star is itself double, but can only be seen with large instruments. 

It is probaljly a binary star, with a period of not more than thirty years. 
A red-coloured 2nd magnitude star, with two faint companions. 



NEBULA AND STAR CLUSTERS. 
M. 15 



4815 
5023 



A globular cluster of mimite stars, visible to the naked eye. 

by Maraldi in 1745. 
A fairly large and bright nebula, with central condensation. 
A scattered cluster of 10th magnitude and fainter stars. 



It has a diameter of about 4', and was discovered 



VARIABLE STARS. 

/3 I An irregular variable star, discovered by Schmidt in 1847. 
7 I Slightly variable, in a period of about 27 days. 
6, I, $, TT, 0, 61, and 80 are thought to be slightly variable. 



Maximum 2'2 ; minimum 2*7. 



DOUBLE STARS. 



Pisces. 



35 I A 6th magnitude star, with a 7"5 magnitude companion, distant 12". 



51 
55 
65 
ylr 

77 

? 
a 



A 5th magnitude star, with a 9tli magnitude companion, at a distance of 28". 
A beautiful coloured double star, magnitudes 5 and 8 ; distance 6" ; colours, yellow and deep blue. 
A double star, whose components are nearly equal in magnitude ; distance 4". 
Also equal in magnitude, distance 30". Easily seen with small telescopes. 
A good object for a small instrument. Magnitudes 6 and 7 ; distance 33". 
Magnitudes 5 and 7 ; distance 23". 

A very beautiful double star, and easily seen bj' aid of a small telescope. Colours, pale green and blue 
magnitudes 3 and 4 ; distance 3". Thought to be a binary star. 



NEBULA AND STAR CLUSTER. 

307 I A round nebula, with bright centre. 

372 1 A faint globular cluster, somewhat spiral in form when viewed with large instruments. 



DOUBLE STARS 



Lacerta. 



10 
13 



A 5th magnitude star, with a companion, distant 15". 

A quadruple star. Magnitudes 6, 6-5, 8-5, and 10 ; distances 22", 28", 67", and 82" 

A 5th magnitude star, with a faint companion, distant 59". 

A 5th magnitude star, with a faint companion, distant 15". 



STAR CLUSTERS. 

4755 I A fairly large and rich cluster of stars, from 8th to 10th magnitudes. 
4773 I A coarsely-scattered cluster of about 16' in diameter. 



DOUBLE STARS. 



Triangulum. 



A 4tli magnitude star, M^th a companion, distant 110". 

A 5th magnitude star, with an exceedingly faint companion, distant 4". 

Magnitudes 5 and 7 ; distance 4" ; colours, yellow and blue. 



STAR CLUSTER. 



M. 33 I A Large, though faint, spiral cluster of stars, discovered by Messier. 
I like a nebula. 



In a small telescope it appears somewhat 



163 



Chart 3. 

Interesting Objects for the Telescope. 



-•4*- 



DOUBLE STAES. 



Auriga. 



4(0,) 

a 

14 

26 

e 

41 
56 
X 



A 5-5 magnitude star of a greenish colour, with a 7th magnitude companion, distant 6". 

Capella. A 1st magnitude star, with several faint companions. 

A triple star. Magnitudes 5-5, 7, and 11 ; distances 15" and 13". 

Also a triple star. Magnitudes 6, 8, and 11 ; distances 12" and 26". 

A quadruple star. Magnitudes 3, 7, 9, and 10 ; distances 2", 45", and 125". 

A 6th magnitude star, with 6-5 magnitude companion, distant 8". 

Magnitudes 6 and 8 ; distance 37", 

A 5th magnitude star, with faint companion, distant 104". 



STAR CLUSTERS AND NEBULA. 



996 

1067 

1101 

1114 

M. 38 

1137 

M. 36 

M. 37 

1451 

VARIABLE 
R 
e 

V 
K 



DOUBLE STARS. 



A rich field of stars from the 7th to 12th magnitudes. 

A very beautiful cluster of small stars. 

A fairly large and rich cluster of small stars. 

A circular cluster of stars, from the 9th to 12th magnitudes. 

A very beautiful circular cluster of stars about 10' in diameter, 

A brilliant circular nebula, about 5' in diameter. 

A cluster of stars from the 7th to 12th magnitudes, and about 9' in diameter. Well seen with a small telescope. 

A large cluster of small stars, with a diameter of nearly half a degree. A magnificent object. 

A somewhat coarse cluster of stars. 

STARS. 

A variable star ; discovered at Bonn in 1862. Maximum magnitude, 6'5 to 7'5 ; minimum 13 ; period 465 days. 
Discovered by Fritsch in 1821. Maximum 3'0 ; minimum 4-5 ; period irregular. 
Thought to be variable from 4*3 to 5 '4. 
Thought to be variable. 

Gemini. 



7 
e 

38 

8 



A 3rd magnitude star of a yellow colour, with a very faint companion, distant 73", 

This 2'5 magnitude star has two exceedingly faint distant companions. 

Magnitudes 3'5 and 8 ; distance 111". 

A 5th magnitude star, with an 8th magnitude companion ; distance 6" ; colours, yellow and blue. 

This 4tli magnitude star has two companions. Magnitudes 7 and 10 ; distances 90" and 65." 

Magnitudes 4 and 10 ; distance 10". 

A yellowish 3'5 magnitude star, with a reddish 8th magnitude companion at a distance of 7", 

Castor. One of the finest double stars in the heavens, and easily seen with a small telescope. Magnitudes 

2-7 and 37 ; distance 5"'5. A binary star, with a period of about 1000 years. 
Pollvx. TJiis brilliant star has no less than five very faint companions. 
Magnitudes 4 and 9 ; distance 6". 
A 4th magnitude star, with an 8th magnitude companion, distant 112", 



STAR CLUSTERS. 

1325 A coarsely-scattered cluster of 7th to 11th magnitude stars, about 7' in diameter, 
M. 35 A most striking object. The cluster is about 20' in diameter, and contains many brilliant stars, 
seen with a small instrument. 
1467 A triangular cluster of small stars. 
1490 A coarsely-scattered cluster of very small stars. 
1549 A mass of very small stars, about 6' in diameter. 

VARIABLE STARS. 



Beautifully 



DOUBLE STARS. 



Discovered by Schmidt in 1865. Maximum 3*2 ; minimum 37 to 4-2 ; period about 229 days. 

Discovered by Schmidt in 1844 to be variable from magnitude 37 to 4-5 in a period of 10'2 days. 

An irregular variable star of a deep red colour. Discovered by Hind in 1848. Maximum 6-5 ; minimum 12, 

Orion. 



14 
P 

/3 



V 
3 



A very close double star. Magnitudes 6 and 7, distance about 1". 

Magnitudes 5 and 9 ; distance 7" ; colours, yellow and bluish white. 

Rigel. Tliis brilliant star has an 8th magnitude companion, distant 10". Well seen with a telescope of 4 

inches aperture. In large instruments the companion has been seen to be double. 
A triple star. Magnitudes 3, 5, and 5 ; distances 1" and 110". 
This 5th magnitude star has a very faint companion ; distance 3". 
A 2nd magnitude star, with a 7th magnitude companion, distant 53". 

154 (ncscripfion of Chart S continued over the next page.) .. 



Chart 




DOUBLE STABS— confinued. O R I O H— continued. 

X Magnitudes 3 and 6 ; distance 4". 

f A triple star. Magnitudes 3, 7, and 9 ; distances 12" and 49". 
<T A multiple star. Magnitudes 4, 6, 7, and 11 ; distances 12", 61", and 12". 

f A very beautiful double star. Magnitudes 2 and 6 ; distance 3". There is another companion of the 10th 
magnitude, at a distance of 53". 
52 A 5th magnitude star, •with a 6th magnitude companion, distant nearly 2". 
23 Magnitudes 5 and 7 ; distance 32". 

Q^ The well-known trapezium in the Great Nebula. Magnitudes 6, 7, 7'5, and 8. These four stars are wnell seen 
with a small instrument. In large telescopes six stars are seen. 

NEBULA AND STAR CLUSTER. 



M. 42 

1227 
1376 



The great Nebula. One of the most wonderful objects in the heavens. Before the spectroscope was applied to it, 
it was supposed to be a cluster of exceedingly faint stars, but is now known to be a mass of incandescent gas. 
A fairly brilliant and extensive nebula, with dark space near centre. 
A cluster of small stars about 6' in diameter. 



VARIABLE STARS. 



Betelgeux. Maximum I'O ; minimum 1*4 ; period irregular. 
Variable from 2'2 to 2'7 in an irregular period. 
TT^, -^j ry, and K are thought to be variable. 

DOUBLE STARS. P E R S E U S. 



A 4th magnitude star, with an 8th magnitude companion, distant 28". 

A 5th magnitude star, with a 9th magnitude companion, distant 20". 

A quintuple 3rd magnitude star. The companions are all very faint. 

Magnitudes 3 and 8 ; distance 9". 

A 4th magnitude star, with an 8th magnitude companion at a distance of 15". 

A 4th magnitude triple star. Distance of principal companion 15". 

This 3rd magnitude star has a faint companion, distant 6". 



STAR CLUSTERS. 

M. 34 A coarsely-scattered cluster of stars, -which can be beautifully seen with small telescopes. 
658 A rich cluster of stars, about 8' in diameter. 
212 and 221 These two large and brilliant clusters of stars form one of the most brilliant telescopic objects in the heavens. 

VARIABLE STARS. 

p An orange -coloured irregular variable star, discovered by Schmidt in 1854. Maximum magnitude, 3'4; 

minimum 4 '2. 
yS Algol. One of the most interesting variable stars. Maximum magnitude, 2-2 ; minimum 3'7 ; period 2 days 
20 hours 48 minutes 54 seconds, 
e and B are thought to be slightly variable. 

DOUBLE STARS. TAURUS. 

7 A 6th magnitude star, with a 10th magnitude companion at a distance of 22". The primary is itself double 

when seen with a very powerful instrument. 
r} The brightest star in the Pleiades. A very beautiful 3rd magnitude quadruple star, and well seen with a small 

telescope. 
30 Magnitudes 5 and 9 ; distance 9". 

^ A 5th magnitude star, with an 8th magnitude companion, distant 56". 
p^ A 6th magnitude star, with an 8th magnitude companion, distant 19". 
K Magnitudes 5 and 6 ; distance 339". 

a Aldebaran. This brilliant star has one or two very faint companions. 
88 Magnitudes 5 and 8 ; distance 69". 

T An easily-divided double star. Magnitudes 4 and 7 ; distance 62". 
Ill Magnitudes 5 and 8 ; distance 75". 
118 Magnitudes 6 and 7 ; distance 5". 
62 Magnitudes 6 and 8 ; distance 29". 

NEBULA AND STAR CLUSTERS. 

1030 A large cluster of faint stars. 

M. 1 The Crab Nebula, near ihe star ^; discovered by Bevis in 1731. 

1199 A large cluster of faint stars of nearly equal magnitude. 

VARIABLE STARS. 

A variable star of the Algol type, discovLiCd by Baxendell in 1848. 

period 3 days 22 hours 52 min. 
Thought to be slightly variable, in a period of about 7 days. 



Maximum magnitude, 3 4; minimum 4*2 ; 



155 



Chart 4. 

I:tTTEiiESTiNG Objects for the Telescope. 



DOUBLE STAE8. 



Canis Minor. 



a 

14 
V 



Procyon. This brilliant star has several very faint companions. 

A 5th magnitude triple star. The magnitudes of the companions are 7 and 8 ; distances 76" and 112". 

A 5th magnitude star, with an exceedingly faint companion at a distance of 4". 



DOUBLE STARS. 



Cancer. 



t 

a'- 
66 



A very interesting triple star. Magnitudes 5, 6, and 5-5 ; distances 1" and 5". 
Magnitudes 6 and 6'5 ; distance 5". An interesting oljject for small telescopes. 
Magnitudes 6 and 7 ; distance 6". 

A 4th magnitude star, with a 6th magnitude companion at a distance of 31". 
A close double star. Magnitudes 6 and 7 ; distance less than 2". 
Magnitudes 6 and 8 ; distance 5". 



STAR CLUSTERS. 



M. 44 
M. 67 



The Prcesepe of the Ancients. A very fine object for small telescopes. 
A cluster of faint stars, forming a very beautiful object. 



VARIABLE STARS. 

K I Discovered to be variable by Schwerd in 1829. Maximum magnitude, 6'5 ; minimum 12 ; period 354 days, 
"^ and i are thought to be variable. 



DOUBLE STARS. 



Leo. 



49 

54 

I 

T 

90 
93 



A 6th magnitude star, with a 9th magnitude companion, distant 39". 

A 6th magnitude star, with an 8th magnitude companion, distant 43". 

This 2nd magnitude yellowish star, has a red 3 '5 magnitude companion at a distance of 3". It is one of the 

finest objects in the heavens, and is a binary star, in a period of 407 years. 
Magnitudes 6 and 9 ; distance 2'5". 

A 4th magnitude star, with a 7th magnitude companion of a bluish colour, at a distance of 6". 
Magnitudes 4 and 7 ; distance 3" ; colours, yellow and blue. 
A 5th magnitude star, with a 7th magnitude companion, at a distance of 95". Well seen with a small 

telescope. 
Magnitudes 6, 7, and 9 ; distances 4" and 64". 

A 4th magnitude star, ^vith an 8th magnitude companion, at a distance of 74". 
A 3rd magnitude star, with a 7th magnitude companion, at a distance of 314". . 



NEBULA. 

2184 Large and round nebula, with condensation near centre. 



2203 

2.301 

M. 65 & M. 66 



Two faint nebulae, with condensation at centre. 

Large oval shaped nebula, with star-like nucleus. 

Two large, though faint, nebulae, somewhat elongated in shape. 



VARIABLE STARS. 

R I Variable from 5th to 10th magnitude, in a period of 313 days, 
f, •>//■, 40, ^, and /3 are thought to be variable. 



DOUBLE STARS. 



Leo Minor. 



7 I A 6th magnitude star, with a companion, at a distance of 55". 
33 I A 6th magnitude star, with a companion, at a distance of 20". 
42 1 A wide 5th magnitude double star ; distance 200". 



158 



{Description of Chart h continued over the next page.) 



NEBULA. 



Leo M I N O Rj— continued. 



2104 I A fairly brilliant nebula, somewhat elliptical in shape. 

2274 I A large and brilliant nebula, which is thought to be a distant star cluster. 

VARIABLE STARS. 

E I Maximum magnitude, 6 to 7'5 ; minimum 11 ; period 375 days. 

DOUBLE STARS L Y N X. 



5 
12 
19 
24 
38 



A triple star ; magnitudes 6, 8, and 10 ; distances 30" and 96". 

A triple star ; magnitudes 5, 6, and 7 ; distances 1"5" and 9". 

Magnitudes 6 and 7 ; distance 15". 

A 5tli magnitude double star ; distance 60". 

A 4th magnitude star, with a 7th magnitude companion at a distance of 3" 



DOUBLE STARS. 



Ursa Major. 

{The remaining part of this Constellation is given on Chart 1.) 



57 
65 



This 3rd magnitude star has a faint companion at a distance of 10". 
A rapid binary star ; magnitudes 4 and 5 ; distance 2" ; period 60 years. 
Magnitudes 5 and 8 ; distance 5". 
Magnitudes 6 and 8 ; distance 4". 



NEBULA. 



1823 
2600 
2841 



A fairly brilliant nebula, about 6' in diameter. 
A bright nebula, with a diameter of about 4". 
A large bright and oval shaped nebula. 



157 



Chart 5. 

Interesting Objects for the Telescope. 



■*$*■ 



DOUBLE STABS. BOOTES. 

1 Magnitudes 6 and 9 ; distance 5". 

fc This 4th magnitude greenish star has a bluish 7th magnitude companion at a distance of 13". 

I A 4th magnitude star, with a 7th magnitude companion at a distance of 38". 

TT Magnitudes 4 and 6 ; distance 7". 

^ Magnitudes 3 and 4 ; distance 1". A difficult object, requiring a very powerful telescope to observe it. 

6 A very beautiful double star. Magnitudes 2 and 6 ; distance 3" ; colours, yellow and blue. 

^ A binary star. Magnitudes 4 and 6 ; distance 4" ; period about 130 years. 

39 Magnitudes 6 and 6 '5 ; distance 4". 

44 Magnitudes 5 and 6 ; distance 5" ; colours, yellow and blue. 

/ti Magnitudes 4 and 7 ; distance 108". 

VARIABLE STAES. 

R j Maximum magnitude 59 to 7'5 ; minimum 11 to 12 ; period about 223 days. 
34 Variable from 5'2 to 61 in a period of about 370 days. 
TT and /i Are thought to be variable. 



DOUBLE STAES 



Canes Yenatici. 



2 

a 

15 and 17 

25 



A 5th magnitude star, with an 8th magnitude companion at a distance of 11". The colours are yellow and blue. 

A 3rd magnitude star, with a 6th magnitude companion at a distance of 20". 

These two 5th magnitude stars, situated from each other 4' 30", form an interesting object for a very small 

telescope. 
Magnitudes 5 and 7, distance 1". 



NEBULA AND STAB 

M. 94 

M. 51 

M. 3 

M. 63 



CLUSTEB. 
A small bright nebula, having the appearance of a comet. 

The wonderful spiral nebula, which requires a large telescope to reveal its starry nature. 
A brilliant globular cluster of not less than 1000 small stars. Well seen with a small telescope. 
A faint oval nebula of about 10' in length. 



DOUBLE STABS 



Coma Berenices. 



2 
12 
24 
35 



A 6th magnitude star, with a 7'5 magnitude companion at a distance of 4" 

Magnitudes 5 and 8 ; distance 66". 

Magnitudes 5 and 6 ; distance 20" ; colours, yellow and blue. 

A triple star. Magnitudes 5, 8, and 9 ; distances 1""5 and 29". 



NEBULA AND STAB CLUSTEBS 

2752 A small globular cluster of stars, densely collected at centre. 

2838 A faint nebula, of a spiral form. 
M. 85 A somewhat faint nebula. 
M. 53 A very beautiful cluster of minute stars. 
M. 64 A large nebula, with very bright nucleus. 



DOUBLE STABS 



Corona. 



? 



A 4th magnitude star, with a 5th magnitude companion at a distance of 6". 
Magnitudes 5 and 6 ; distance 4" ; colours, yellow and blue. 



V A 5th magnitude star, with four faint companions.- 



VARIABLE STABS. 



Variable from magnitude 5-8 to 13, in a period of about 359 days. 
Maximum magnitude 6 to 8 ; minimum magnitude 12 to 13 ; period 361 days. 
Variable from 2'0 to 9-3. A temporary star whose last maximum brilliancy was in May, 1866. 
l>i (Description of Chart 5 continued on next page.) 



Chart 




Serpens. 

DOUBLE STARS. 

5 A 5th nicagnitude double star ; distance 10". 

h A 3rd magnitude star, witii a 4th magnitude companion at a distance of 3". 

/3 Magnitudes 3 and 9 ; distance 31". 

49 Magnitudes 6 and 7 ; distance 4". 



Thought to be a binary star. 



STAB CLUSTER. 

M. 5 I A beautiful assemblage of very small stars, somewhat condensed near the centre. 

159 



Chart 6. 

Interesting, Objects for the Telescope. 



C Y G N U S. 

DOUBLE STABS. 

^ ; A very beaiitifiU object for sniall telescopes. Magnitudes 3 and 5 ; distance 34" ; colours, orange and blue. 



16 

a 

17 

32 
49 
52 
61 



Magnitudes 6 and 6 ; distance 37". 

A double star, but very difficult to observe. The companion is of the 8th magnitude, and is distant from the 

primary less than 2". 
A reddish 6th magnitude star, with a blue 8th magnitude companion at a distance of 26". 
Magnitude 6 and 7'5 ; distance 3". 

A triple star. Magnitudes 5, 5, and 7 ; distances 338" and 107". 
Magnitudes 6 and 8 ; distance 3". 

A 4th magnitude star, with a 9th magnitude companion at a distance of 6". 
One of the first stars whose distance has been determined {see CJiapter 3). The magnitudes are 5 and 6 ; 

distance 20". 
Magnitudes 5 and 6 ; distance 4". There is also another companion at a distance of 217". 



STAB CLUSTEBS. 



4544 

4575 

M. 39 



A rich star cluster 15' in diameter. 

A fine cluster of small stars. 

A large and brilliant cluster of stars. 



VABIABLE STABS. 



63 
R 

X 
P 

T 

V 



Thought to be variable from magnitude 4'7 to 6'0. 

Variable from the 6tli to the 13th magnitude, in a period of about 425 days. 

Discovered by Kirch in 1686. Maximum magnitude, 4 to 6 ; minimum 13 ; period about 406'5 days 

A 6th magnitude star, which in the year 1600 increased to the 3rd magnitude. 

Variable from magnitude 5 '5 to 6 in an irregular period. 

Thought to be variable. 



DOUBLE STABS. 



Delphinus. 



This 3rd magnitude star has a faint companion at a distance of 32". 

A 5th magnitude double star ; distance 13". 

A 4th magnitude star, with a 9th magnitude companion at a distance of 35". 

Magnitudes 4 and 5 ; distance 12". Well seen with a very small telescope. 

E Q U U L E U S. 



DOUBLE STABS 

e A 5th magnitude star, with a 7th magnitude companion at a distance of 11". The primary has been found to 



be an exceedingly close double star. 
Magnitudes 6 and 6 ; distance 3". 

A triple star. Magnitudes 5, 6, and 10 ; distances 366" and 2". 
Also a triple star. Magnitudes 5, 10, and 10 ; distances 0"'5 and 23". 



Hercules. 

double stabs 

K A 5th magnitude star, with a sixth magnitude companion at a distance of 31". 

7 A 4th magnitude double star ; distance 39". 

m An easily divided double star. Magnitudes 6 and 6 ; distance 69". 

^ A rapid binary star. Magnitudes 3 and 6 ; distance less than 2" ; period 35 years (see Blate of Double Stars). 

a Magnitudes 3 and 6 ; distance 5". 

8 Magnitudes 3 and 8 ; distance 19". 

p Magnitudes 4 and 6 ; distance 4". Thought to be a binary star. 

fi A 3rd magnitude star, with a 9th magnitude companion at a distance of 31". The companion is an exceedingly 

close double star. 
95 Magnitudes 5 and 5 ; distance 6". 

no {Description of Chart 6 continued over the next page.) 



Chart 




STAB CLUSTERS. 



H E R C U L E S— continued. 



M. 31 



M. 92 



One of the finest globular clusters in the heavens. Discovered by Halley in 1714, This magnificent object 

can be fairly well seen with a small telescope. 
A very fine cluster, with intensely bright centre. 



VARIABLE STARS. 



U 

30 
S 
a 



Variable from magnitude 6 to 11 in a period of 408 days. 

An irregular variable star. Maximum magnitude 5 ; minimum 6'2, 

Maximum magnitude, 6 to 7 ; minimum 12 ; period 303 days. 

Variable from 3'1 to 3'9 in an irregular period. 

Variable from 4*6 to 5"4 in a period of 38'5 days. 



DOUBLE STARS. 



Lyra. 



Vega. This brilliant star, has several very faint companions. 

One of the most interesting double stars in the heavens. With a very small instrument the two stars are 
easily seen, being situated at a distance of 200". In a telescope of three or four inches aperture, how- 
ever, each star is seen to be double ; distances 3" and 3" ; magnitudes 4 and 6, and 5 and 5. 

Magnitudes 4 and 5 ; distance 44". 

A triple star, whose magnitudes are 4, 7, and 8, at distances of 46" and 66". 



1} I A bluish 4th magnitude star, with a faint comiDanion at a distance of 28". 



NEBULA. 



M. 57 I The only ring nebula that can be seen with a small telescope. 
M. 56 A faint resolvable nebula of about 5' in diameter. 



VARIABLE STARS. 

, R I Variable from 4'3 to 4'6 in a period of 46 days. 

^ I Variable from 3'4 to 4-5 in about 12 days 22 hours. 

Sag ITT A. 

DOUBLE STARS. 

e A. 6th magnitude star, with an 8th magnitude companion at a distance of 92". 
^ Magnitudes 6 and 9 ; distance 8". In large instruments the primary is seen to be a close double. 
13 Magnitudes 6 and 7 ; distance 29". 
6 A triple star. Magnitudes 6, 8, and 8 ; distances 11" and 70". 

NEBULA. 

M. 71 I A large, though faint nebular mass. 

VULPECULA. 

DOUBLE STAR. 

6 I A wide double star. Magnitudes 4 and 5 ; distance 403". 

NEBULA AND STAR CLUSTER. 

M. 27 The Dumb-Bell Nebula, visible with a very small telescope. With large instruments it appears a mag- 
nificent object (see Plate of Nebula;). 
4559 A rich cluster of stars, from the 6th to 13tli magnitude. 

161 



Ji 



Chart 7. 
Ils^TERESTING OBJECTS FOR THE TELESCOPE. 



— <^ — 

DOUBLE STABS. C E T U S. 

26 Magnitudjes 6 and 9 ; distance 16". 

42 A close double star. Magnitudes 6 and 7. 

X A 5tli magnitude star, with a 7tli magnitude companion at a distance of 3". 

V A 5th magnitude star, with a 9th magnitude companion at a distance of 8". 

7 A yellow-coloured 3'5 magnitude star, with a 6th magnitude companion, at a distance of 3". 

12 A 6th magnitude double star ; distance 9". 

37 A 5th magnitude star, with a 7th magnitude companion, at a distance of 50". 

58 A 6th magnitude star, with a very faint companion at a distance of 3". 

61 A 6th magnitude star, distance 39". 

66 Magnitudes 6 and 8 ; distance 15". 

84 A 6th magnitude star, with a companion, at a distance of 5". 

94 A 5th magnitude star, with a very faint companion, at a distance of 5". 



NEBULA. 
H. 342 

M. 77 



A small faint nebula, with bright centre. 
A small faint nebula. 



VARIABLE STABS. 

Mira. One of the most remarkable variable stars in the heavens. Discovered by Fabricus in 1596. At the 
maximum the magnitude varies from 1"7 to 5*0, and at the minimum from the 8th to 9th magnitude. 
Period 331 days 8 hours 4 minutes. 



COLUMBA. 

DOUBLE STARS 

j A 5th magnitude star, with an 8th magnitude companion. 
B.A.C. 2079 I A 5th magnitude triple star. Distances 12" and 70". 

STAB CLUSTEBS. 

H. 1009 I A bright resolvable cluster. 

H. 1061 I A bright cluster of small stars, condensed near centre. 

BED STAR. 

V I A very red-coloured 4th magnitude star. 



DOUBLE STABS. 



Caelum. 



B.A.C. 1389 
7 



Magnitudes 6*5 and 6-5 ; distance 7". 

A 5th magnitude star, with a 7th magnitude companion. 

Magnitudes 5 and 7 ; distance 14' — forming 71 and 7^. 



DOUBLJ, STAB,. E R I D A N U S. 

A 3rd magnitude star, with a 5th magnitude companion, at a distance of 9". 

A 6th magnitude double star ; distance 3". 

A 4th magnitude star, with a faint companion at a distance of 5". 

Magnitudes 5-5 and 5; distance 9". 

A 5th magnitude star, with a faint companion at a distance of 8". 

Magnitudes 5 and 6 ; distance 6". 

Magnitudes 5 and 10 ; distance 7". 

Magnitudes 5 and 9 ; distance 84." The bright star is again double ; distance 3". 

Magnitudes 7 and 7-5; distance 10". 

A 6th magnitude star, with a 9th magnitude companion ; distance 63". 

Magnitudes 5 and 6 ; distance 9". 

1''3 (Description of Chart 7 continued over the next page.) 



<f> 
P' 

f 

30 
32 
39 

o2 

55 
62 

e 



CHART 7. 




E R I D A N U S— continued. 
COLOURED STAB. 

i|r I A remarkable blue-coloured star. 

VARIABLE STARS. 

60 Variable from 5th to 6th magnitude, 
R Variable from 5th to 6th magnitude. 
S Variable from magnitude 4'6 to 5 ■5. 

NEBULA. 

H. 826 I Bright planetary nebula. 



DOUBLE STARS. 



Fornax. 



x' 



Magnitudes 5 and 8; distance 11". 

Magnitudes 6 and 7 ; distance 5". 

Magnitudes 3 and 8; distance 4". 

A 6th magnitude star, with a 10th magnitude companion. 



NEBULA AND STAR CLUSTERS. 

H. 697 Bright nebula, with star-like centre. 
H. 744 A bright cluster of small stars. 
H. 769 A brilliant cluster of small stars. 

VARIABLE STARS. 

V I A 6th magnitude variable star. 
%'^ I Variable from 5th to 6th magnitude. 

Sculptor. 

DOUBLE STARS. 



h 
B.A.C. 306 

e 



A 5th magnitude star, with a 7th magnitude companion. 

A 4th magnitude star ; distances 3" and 74". 

A 6th magnitude star, with a faint companion at a distance of 9". 

Magnitudes 6 and 6 ; distance 1". A close double star. 

Magnitudes 6 and 10; distance 6". 



VARIABLE STAR. 

R I One of the most brilliantly-coloured stars in the heavens. The colour is of an intense scarlet. ^laximum 5-8; 
I minimum 77. 

STAR CLUSTER AND NEBULA. 

H. 162. 1 A bright cluster of small stars, from the 12th to the 16th magnitude, with a diameter of about 5'. 
H. 361 I A large and faint elongated nebula, with bright centre. 

163 



Chart 8. 

Interesting Objects for the Telescope. 



►$*- 



DOUBLE STARS. CANISMAJOR. 

a Sirius. This brilliant star has a 10th magnitude companion at a distance of 10". It cannot, however, be seen 
with any but the largest telescopes. 

6 Magnitudes 6 and 8 ; distance 17". 
19 A 5th magnitude star, with a 10th magnitude companion. 

/i Magnitudes 5 and 8 ; distance 4". 

30 A triple star. Magnitudes 4-5, 9, and 9 ; distances 8" and 15", 
7^ Magnitudes 6 and 8; distance 17". 

STAR CLUSTERS. 



M. 41 
H. 1512 



A splendid group of small stars, visible to the unaided eye as a 5th magnitude star. 
A beautiful cluster of 10th magnitude stars. 



VARIABLE STARS 

qI Variable from magnitude 3-8 to 4'2. 

22 An exceedingly red 4th magnitude star, which is thought to vary slightly in magnitude. 
27 Variable, in a long period, from magnitude 4"5 to 6"5. 
R A variable star of the Algol type, and of the 6th magnitude ; period 1 day 3 hours 16 minutes. 



DOUBLE STARS. 



Hydra. 



9 

p(13) 
17 

e 

27 

t1 (31) 

X 

/3 

52 
54 



A 5th magnitude star, with a faint companion at a distance of 35". 

A 3rd magnitude binary star. The companion is of the 8th magnitude at a distance of 3". 

A 5th magnitude star, with an exceedingly faint companion at a distance of 12". 

Magnitudes 6 and 7 ; distance 5". 

A 4th magnitude star, with faint companion at a distance of 53". 

Magnitudes 5 and 7 ; distance 226". 

Magnitudes 5 and 8 ; distance 65". 

A 4th magnitude star, with a companion at a distance of 51". 

A 4th magnitude double star ; distance 2". 

A 5th magnitude star, with a faint companion at a distance of 4". 

Magnitudes 5 and 7 ; distance 10". 



NEBULA. 

H. 2102 I A planetary nebula, having much the same appearance as the planet Jupiter. 

VARIABLE STARS. 



Variable from 4'5 to 6th magnitude. 

Variability discovered in 1874 by Maraldi. The variations range from magnitude 4"5 to 10"5, in a period of 
469 days. 



DOUBLE STARS. 



L E P U S. 



A 5th magnitude star, with a 10th magnitude companion at a distance of 15". 
A 5th magnitude star, with an 8th magnitude companion at a distance of 3". 
A 3rd magnitude double star ; distance 3". 
A 3rd magnitude double star ; distance 36". 
Magnitudes 4 and 7 ; distance 94". 



STAR CLUSTERS. 



M. 79 
H. 3780 



A bright cluster, about 3' in diameter. 

A brilliant group of small stars, well seen with a small telescope. 



VARIABLE STARS. 



R 



Variability discovered by Schmidt in 1855. The variations of magnitude range from the 6th to the 8"5 

magnitude, in a period of 438 days. 
Thought to be variable. 

IS* (Description of Chart 8 continued over the next page.) 



Chart 




DOUBLE STARS. 



MONOCEROS. 



3 

5 

e(8) 

10 

^(11) 
29 
30 



A 5th magmtude star ; distance 2". 

A 4th magnitude star ; distance 35". 

Magnitudes 5 and 7 ; distance 13". 

A triple star. Magnitudes 5, 9, and 10 ; distances 76" and 81". 

A triple star. Magnitudes 5-5, 5'5, and 6 ; distances 7" and 10". 

A 5th magnitude triple star ; distances 32" and 67" ; magnitudes 6 and 11. 

A 4th magnitude double star : distance 91". 



STAB CLUSTERS. 



H. 1637 

H. 1424 

M. 53 



A group of 9th magnitude stars, visible to the naked eye. 
A beautiful cluster of small stars, visible to the naked eye. 
A brilliant cluster of stars, half-a-degree in diameter. 
The star 10 is the centre of a beautiful cluster. 



VARIABLE STARS. 

T Variability discovered by Gould in 1871. 



S(15) 
U 



The variation is from the 6th to the 8th magnitude, in a period of 
2-7 days. 
Variability discovered in 1867. Maximum magnitude, 5 ; minimum 5-5 ; period 3-4 days. 
Variability discovered by Gould in 1873. Maximum magnitude, 6 ; minimum 7 ; period 46 days. 



DOUBLE STARS. 
B.A.C. 1964 
V 



(Argo) Puppis. 

Magnitudes 6 and 6 ; distance 2' 30". 

Magnitudes 5 and 7 ; distance 13". 
77 A 3rd magnitude star, with an 8th magnitude companion, 
o" Magnitudes 3"5 and 9 ; distance 22". 
2 Magnitudes 7 and 7 ; distance 17". 
5 Magnitudes 6 and 9 ; distance 4". 

VARIABLE STARS. 

L. 2 Variable from the 4th to the 6th magnitude, in a period of 136 days. 
77 Variable from magnitude 2 '3 to 3'3. 
T Variable from the 6th to the 7th magnitude. 



16S 



2 A 



Chart 9. 

Interesting Objects for the Telescope. 



DOUBLE STAES. 



A N T L I A. 



A 5th magnitude star, with a 6th magnitude companion at a distance of 8". 
Magaitudes 6 and 10 ; distance 11". 



VARIABLE STARS. 

R I Variable from the 6th to the 8th magnitude. 

7 I Thought to be variable from the 5th to the 7th magnitude. 



DOUBLE STARS. 



C O R Y U S. 



S j A 3rd magnitude star, with a faint companion at a distance of 24". 
L. 23675 I A 5th magnitude star, \vith a 6th magnitude companion at a distance of 5". 



NEBULA. 

H. 2917 I A faint resolvable nebula. 



DOUBLE STARS. 
D 



Centaurus. 



Magnitudes 6 and 7 ; distance 4". 

A close double star of the 3rd magnitude ; distance 1". 

A 5th magnitude star, with a 10th magnitude companion at a distance of 26". 

A 5th magnitude star, with a 7th magnitude companion at a distance of 5". 

Magnitudes 5 and 10 ; distance 25". 

Magnitudes 6 and 7 ; distance 18". 

Magnitudes 5 and 6 ; distance 9". 

Magnitiides 5 and 7 ; distance 14". 

A well-known binary star. Magnitudes 1 and 3'5 ; distance 16", The nearest known star to our system. 

A triple star ; magnitudes 6, 8, and 11 ; distances 10" and 35". 



STAR CLUSTER. 

H. 3531 I A cluster of small stars, 20' in diameter, visible to the naked eye. One of the finest objects in the heavens. 



DOUBLE STARS. 



Sextans. 



35 

41 

9 



Magnitudes 6 and 8 ; distance 7". 

Magnitudes 5 and 8 ; distance 27". 

Magnitudes 6 and 7 ; distance 50" ; colours, yellow and blue. 



Virgo. 

DOUBLE STARS. 

y A remarkable binary star ; distance 5"; magnitudes 3'5 and 3*5 ; period 185 years, 

d^ A 6th magnitude double star, with a faint companion at a distance of 4". 

k A 6th magnitude star, with a companion at a distance of 21" 

$ Triple star. Magnitudes 5, 9, and 10 ; distances 1" and 71". 

53 Magnitude 5 ; distance 71. 

54 Magnitudes 6'5 and 7" j distance 6". 
72 Magnitudes 6 and 9 ; distance 30" 

75 A 6th magnitude star, with a companion, at a distance of 73". 

o (84) A 6tli magnitude star, with an 8th magnitude companion at a distance of 3" ; colours, yellow and blue. 

T (93) A 4th magnitude star, with a companion, at a distance of 80" 

(j) Magnitudes 5 and 9 ; distance 5". 

17 Magnitudes 6 and 9 ; distance 20". 

166 {Description of Chart 9 continued over the next page.) 



Chart 0. 




NEBULM. 

M. 60 

M. 49 

M. 88 

H. 3132 



V I R G O — continued. 



Extremely faint nebula. 
A bright resolvable nebula. 
Spiral nebula of tbe Earl of Rosse. 
A large but faint nebula. 



VARIABLE STARS. 



Variability discovered by Harding in 1809. Maximum magnitude, 6 to 7 ; minimum 11. 
Discovered by Hind in 1802. Maximum magnitude, 6 to 8 ; minimum 12. Period 374 days. 



107 



Chart 10. 

Interesting Objects for the Telescope. 



Corona Australis. 

DOUBLE STABS. 

K I Magaitudes 6 and 6 ; distance 22". 

7 I A 5th magnitude binary star ; distance 3" ; pencd 82 years. 



DOUBLE STARS 



Lupus. 



G. 1614 
a 

K 

r 

e 
D 

V 
f 



Magnitudes 6 and 9 ; distance 4". 

A 5th magnitude star, with a 7th magnitude companion at a distance of 20". 

Magnitudes 4 and 6 ; distance 27". 

A 4th magnitude star, with a companion at a distance of 72". 

A triple star. Magnitudes 6, 6, and 8 ; distances 2" and 23". 

Magnitudes 4 and 9 ; distance 26". 

A close 5th magnitude double star. The companion is of the 7th magnitude, and at a distance of 2". 

Magnitudes 6 and 6 ; distance 11". 

Magnitudes 4 and 8 ; distance 15". 

Magnitudes 5 and 9 ; distance 3". 



STAB CLUSTERS. 



H. 3922 
H. 4066 
H. 4100 



A bright cluster of faint stars, from the 9th to the 13th magnitude. 

A faint planetary nebula. 

A cluster of small stars, of the 11th magnitude. 



B.A.C. 5218 
,1 



DOUBLE STARS. 

Magnitudes 6 and 9 ; distance 21". 
Magnitudes 5 and 8 ; -distance 10". 
Magnitudes 5 and 7 ; distance 24". 

STAR CLUSTERS. 



Norma. 



H. 4162 
H. 4170 
H. 4184 



A large and beautiful cluster of small stars, 20' in diameter. 

A coarse and brilliant cluster of stars, from the 7th to the 10th magnitude. 

A bright cluster of small stars. 



Ophiuchus. 

DOUBLE STARS. 

^lr A 5th magnitude star, with a faint companion at a distance of 33'. 

X A close binary star ; period 234 years ; distance 2". 

19 Magnitudes 6 and 8 ; distance 22". 

36 Magnitudes 5-75 and 5'75 ; distance 5". A binary star. 

(39) Magnitudes 6 and 7 ; distance 12". 

53 Magnitudes 6 and 8 ; distance 41". 

61 Magnitudes 6 and 6 ; distance 20". 

67 A 4th magnitude star, with an 8th magnitude companion at a distance of 58". - 

T A close binary star of the 5th magnitude ; period 218 years. The companion is of the 6th magnitude, 

70 A binary star of the 4th magnitude. Period 94 years ; distance 3". 

74 A 5th magnitude double star ; distance 28".' 

VARIABLE STARS. 

Nova {of 1848), 



U 



A temporary star, which appeared in April, 1848 ; the maximum brilliancy was of the 5th 
magnitude ; the present magnitude being about 12'5. 
Discovered to be variable in 1881 from the 6th to the 7th magnitude, in the short period of 21 hours. 



STAR CLUSTERS. 



M. 23 
M. 12 
M. 10 
M. 19 



A beautiful cluster of 10th magnitude stars. 
A resolvable cluster of small stars. 
A Ijrilliant cluster of small stars. 
A large mass of minute stars. 

183 {Description of Chart 10 continued over the next page.) 



Chart 10. 



CO 

o 



H 
X 
tn 

Z 
o 

71 

-i 
X 



X 
o 
a> 

N 

O 

z 



H 
I 
m 

w 
o 

c 

H 
I 

m 

3) 

z 

X 
tn 

S 

CO 

•o 

X 

tn 
n 
m 




X 
H 

o 

z 

u 

I 
h- 



o 

X 



I CO 



Sagittarius. 

DOUBLE STABS. 

A triple star of the 4tli magnitude; distances 40" and 45". The magnitudes of the companions are 9 and 10. 

Magnitudes 6 and 9 ; distance 6". 

A 3rd magnitude double star ; distance 4". 

A 5th magnitude double star ; distance 29". 

Magnitudes 4 and 7 ; distance 29". 

A triple star. Magnitudes 5, 8, and 8 ; distances 36" and 46". 



16 
V 

54 



VABIABLE STABS. 



w 

y 

51 



Variable from the 4th to the 6th magnitude, in a period of 7 days. 

Discovered in 1866 to be variable from the 5th to the 6th magnitude, in a period of Ih days. 

Variable from magnitude 5'5 to 6'5, in a period of 5 days 18 hours. 

Variable from magnitude 5 to 6"5. 



STAB CLUSTEBS. 



M. 


24 


M. 


22 


M. 


25 


M. 


75 


M 


[.8 


DOUBLE 


ST 


A (2) 
^(51) 

11 



A cluster of faint stars. 

A beautiful cluster of faint stars. Well seen with a small telescope. 

A coarse and brilliant cluster of small stars. 

A resolvable cluster, with bright centre. 

A magnificent object for a small telescope. 

Scorpio. 

iBS. 

Magnitudes 5 and 7 ; distance 3". 

A close binary star of the 4th magnitude ; period 96 years. 
A triple star. Magnitudes 2, 5, and 10 ; distances 13" and 1". 
A 6th magnitude double star ; distance 4". 
Magnitudes 3 and 9 ; distance 20". 

Antares. Magnitudes 1 and 7 ; distance 4". Colours, fiery red and green. 
Magnitudes 4 and 7 ; distance 40". 



STAB CLUSTEBS. 



M. 80 
M. 4 

H. 4307 
M. 6 

H. 4340 



A rich and condensed mass of stars, shaped somewhat like a comet. 

A large and faint resolvable cluster. 

A large and dense cluster of minute stars. 

A bright cluster of stars, from the 7th to the 10th magnitude. 

A brilliant cluster of stars, from the 7th to the 12th magnitude. 



169 



2 B 



Chart 11. 

lNTERESTi:^rG Objects for the Telescope. 



DOUBLE STABS. 



Aquarius. 



12 
ylr 
107 
29 
41 
94 

t1 
53 



A binary star. Magnitudes 4 and 4 ; distance 4". Well seen with a small telescope. 

Magnitudes 6 and 7 ; distance 3". 

Magnitudes 5 and 9 ; distance 50", 

A supposed binary star. Magnitudes 6 and 7 ; distance 6". 

Magnitudes 6 and 8 ; distance 5". 

Magnitudes 6 and 8 ; distance 5". 

A 5th magnitude star, with a 7th magnitude companion at a distance of 14". 

Magnitudes 6 and 9 ; distance 30". 

Magnitudes 6 and 6; distance 10". 



VABIABLE STABS. 



T(71) 

R 

NEBULA. 
M. 2 
H. 462 



Thought to be variable from magnitude 4'5 to 6. 

An irregular variable star discovered in 1811. Maximum magnitude 6; minimum 10; period about 390 days. 



A large round nebula. Well seen with a small telescope. 

An elliptical planetary nebula, of a pale blue colour, which has been shown by the spectroscope to be a mass 
of incandescent gas. 



Capricornus. 

DOUBLE STABS. 

IT A 5th magnitude star, with a companion, at a distance of 3". 
/3(11) Magnitudes 5 and 7 ; distance 4". . 

a A fine object for a small telescope. Magnitudes 3 and 4 , distance 370". Both stars are of a yellow colour. 
/8 Magnitudes 3 and 7 ; distance 205" ; colours, yellow and light blue. Also a fine object for a small telescope, 
o'^ Magnitudes 6 and 7 ; distance 22". 

NEBULA. 

M. 30 I A fairly bright comet-like nebula. 

MiCROSCOPIUM. 

DOUBLE STAB. 

a I A 5th magnitude star, with a 9th magnitude companion, at a distance of 22". 



DOUBLE STABS 



PiSCIS AUSTRALIS. 



A 5th magnitude star, with an exceedingly faint companion, at a distance of 25". 

A close 5th magnitude double star. The distance of the 6th magnitude companion from the primary is less 

than 2". 
Magnitudes 4 and 6 ; distance 29". 

A 4th magnitude star, with a faint companion, at a distance of 4". 
Magnitudes 4 and 9 ; distance 5". 

]70 



Chart 11. 



CO 

o 

m I 

z 
m 

> 



H 
Z 

m 
Z 

o 

H 

Z 

n 



I 
o 

N 

o 

z 



H 
Z 
tn 

CO 

o 

c 

H 
Z 
m 

z 

I 
m 
3 

m 

TJ 

z 
tn 

m 




2 

ce 

UJ 

I 
I- 
ir 
o 
z 



m 

I 
H 

O 
CO 

ui 

I 
H 






Chart 12. 

Interesting Objects for the Telescope. 



«^*- 



DOUBLE STARS. A R A. 

H. 4876 Magnitudes 6 and 7 ; distance 10". 
H. 4901 Magnitudes 6 and 7 ; distance 3". 
H. 4949 A 6th magnitude triple star. Distances 3" and 104". 

VARIABLE STAR. A P U S. 

I Variable from tlie 5tli to tlie 6tli magnitude. 

DOUBLE STAR. C I R C I N U S< 

a I Magnitudes 4 and 9 ; distance 16". 

DOUBLE STARS. C R U X. 

A triple star. Magnitudes 1, 2, and 6 ; distances 6" and 90". 

A 2nd magnitude star, with a 5th magnitude companion at a distance of 100". 



DOUBLE STAR. CHAMAELEON. 

€ 1 Magnitudes 5 and 7 ; distance 2". 

DOUBLE STARS. (ARGO) CARINA. 



Magnitudes 3 and 7 ; distance 5". 
Magnitudes 5 and 7 ; distance 15". 



VARIABLE STABS. 

g Variable from the 4th to the 6th magnitude. 

K A remarkable variable star, varying from magnitude 4-5 to 10 in a period of 313 days. 
1 Variable from the 4th to the 5th magnitude in a period of 31 days. 

STAR CLUSTER. 

H. 2167 I A splendid cluster of small stars, visible to the naked eye. 

VARIABLE STAR. D O R A D O. 

E 1 A very red star, which varies from magnitude 5 to 6-5. 

RED STAR. G R U S. 

TT I A very red star of the 6th magnitude. 

DOUBLE STAR. INDUS. 

I A 5th magnitude double star, with a 7th magnitude companion, at a distance of 4". 

DOUBLE STARS. M U S C A. 

H. 4498 A 6th magnitude double star ; distance 9". 

/3 A very close double star ; distance less than 1". Only to be seen with a very powerful telescope. 
6 Magnitudes 6 and 8 ; distance 5". 

DOUBLE STAR. N O R WI A. 

e I Magnitudes 5 and 7 ; distance 27". 

DOUBLE STARS. O C T A N S. 

/-i^ I Magnitudes 6 and 7 ; distance 20". 
A- 1 Magnitudes 6 and 8 ; distance 4". 

(Description of Chart 13 continued over the next page.) j»j 



DOUBLE STARS. 



P I C T O R. 



H. 77 
H. 3835 



Magnitudes 6 and 6 '5; distance 12". 
Magnitudes 6 and 7 ; distance 39". 
Magnitudes 7 and 7 ; distance 6". 
Magnitudes 6 and 6 ; distance 3". 



DOUBLE STAB. 

H. 5222 I Magnitudes 6 and 6 ; distance 3". 



Payo. 



VARIABLE STAR. 

K I Variable from the 4tli to the 5th magnitude, in a period of 9 days. 

STAR CLUSTER. 

H. 4467 I A cluster of very faint stars, visible to the naked eye. 



DOUBLE STARS. 

Magnitudes 6 and 7 ; distance 5". 



Phoenix. 



Magnitudes 4 and 8 ; distance 6". 

A 3rd magnitude star, with an exceedingly faint companion, at a distance of 30". 



DOUBLE STARS. 



Reticulum. 



D. 12 

e 



Magnitudes 6 and 8 ; distance 19". 
Magnitudes 6 and 7 ; distance 5". 



Telescopium. 



DOUBLE STARS. 

H. 5041 j Magnitudes 6-5 and 6-5 ; distance 3". 
D. 227 I Magnitudes 6 and 7 ; distance 23". 

VARIABLE STAR. TRIANGULUM. 

E I Variable from the 6th to the 7th magnitude, in a period of 3 days 9 hours 35 minutes. 



DOUBLE STARS. 

/3 I Magnitudes 5 and 5 ; distance 28". 
A, I Magnitudes 6 and 8 ; distance 21". 



Toucan. 



DOUBLE STARS. V O L A N S. 

Magnitudes 4 and 7 ; distance 6". 

A 4lh magnitude star, with a very faint companion, at a distance of 7". 
Magnitudes 4 and 4 ; distance 28". 
Magnitudes 6 and 7; distance 21". 
Magnitudes 7 and 7 ; distance 4" 
Magnitudes 5 and 7 ; distance 5". 
Magnitudes 5 and 7; distance 13". 



e 

8 
/8 

H. 3416 

K 

7 



STAR CLUSTER. 

H. 52 (^) I One of the grandest clusters in the heavens, visible to the naked eye, as a 4th magnitude star. 

DOUBLE STARS. (ARGO) VELA. 

7 A triple star. Magnitudes 2, 5, and 7 ; distances 41" and 62". 

A A 5th magnitude triple star. Distances 4" and 20". 

b A 4th magnitude double star, with an 11th magnitude companion, at a distance of 7". 

H. 4188 Magnitudes 6 and 7; distance 3". 

H. 4220 A 5th magnitude double star ; distance 3". 

B.A.C. 339G Magnitudes 6 and 8; distance 6". 

J A triple star. Distances 7" and 37". Magnitudes 5, 8, and 9. 

8 Magnitudes 6 and 6; distance 14". 

T A triple star. Magnitudes 5, 10, and 10; distances 7" and 37". 

152 



165 



150' 



135' 



120° 



105* 




T^ i ghtr AsccjiSLon. / in Kqtits 



10 


10 

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Chart 13. 


Bight Ascension 76' in Degrees 60° 45° .jO' 15' 0' 






1 








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. Venus " , . 


«o •' 


. .Wjw . .' _ I 




. JiipitfT . . ...,.„ 1 


40 












, . . Saturn . , , 1 


Ri^hl Ascension 17 in Hours 16 15 14 13 12 


1 



f.y^,iv,a 6> ^-.vW'ji.; .i/>fc-* j.i^.r 



m:mi^'M.m^ 



Aberration of Light, . . , 
„ constant of, . . 

Achromatic Telescope, 
Achromatism, Tests for, . 

Adams, 

Aerolites, 

Algol, Variation of Magnitude of, 
Almegest, Ptolemy's, 
Altitude and Azimuth Instrument, 
Andromeda, Nebula of, . 
Andromedes I. and II. (Meteor SyS' 

tems), ..... 
Annual Motion of the Earth, . 
Annular Nebula in Lyra, . 
Anomalistic Month, . 
Apertures of Telescopes, dividing 

power of, 

Apogee, 

Appian, 

Apsides, Line of, . . . 
Aquarids (Meteor System), 
Aquilids (Meteor System), 

Aratos 

Argelander, .... 
Argus 71, the Variable Star, 
Ariel, the inner Satellite of Uranus, 
Aries, first point of, . 
Arietids (Meteor System), 
Aristarchus, .... 

Aristillus, 

Asteroids, or Minor Planets, 
„ Mass of all the, 
„ Principal Facts 
the. 

Astrolabe, 

Atlas, and the Sphere of Eudoxos, . 
Attraction, Intensity of, on the Moon, 

75 ; Planets, 62 ; Sun, . 
Aurigids (Meteor System), 
Auzot, ...... 

Axis of the Earth, Direction of, 

„ „ Disturbed by Pre- 

cession, . . 



PAGE 

15 

16 

96 

109 

59 

70 

26 

112 

107 

29 

69 

12 

29 

73,80 

111 

74 
67 
73 
69 
69 
112 
114 
26 
62 
15 
69 
33,91 
91 
51 
52 



about 



61, 62 

92 

. 1,3 

35 

69 

100 

13 

13 



B.A.C., contraction foi 


British A 


5S0- 


elation Star Catalogue, . 




. 114 


Bayer, 






112, 115 


Berosus, Hemisphere 


Df, '. 




. 90 


Bessel, 






19, 108 


Biela's Comet, . 






68,70 


Binary Stars, . 






24, 25 


Bode's Law, 






51,59 


Bradley, . 






15, 16 


Brah6, Tycho, . 


.63, f 


)3, 


100, 112 


British Association 


Catalogu 


e 


of 


Stars, . 


. 




. 114 



PAGE 

Calypso, the outer Satellite of Jupiter, 62 
Cassegrainian Telescope, ... 98 

Cassini, 34 

Cassini's Division of Saturn's Ring, 56, 57 
Catalogue of Stars, . . . .127 
Ceres (Minor Planet), ... 51 
Charts of the Stars, Explanation of, 

112,114, 115 

Chromatic Aberration, ... 95 

„ „ Tests for, . 109 

„ Telescope, . . 94, 95 

Chromosphere, the Solar, ... 37 

Chronograph, 101 

Circle, Origin of the Division of the, 2, 91 

„ Meridian or Transit, . . 102 

Classification of Stars, ... 23 

Clepsydra, 93 

Clocks, Observatory, . . . 102 

„ Mean Time and Sidereal, . 103 

Clusters of Stars, ... 28, 29 

Coma of Comets, .... 67 

Comets, 63 

„ Acceleration of, . . . 66 
„ Belonging to the Solar Sys- 
tem, Table of, . . . 65 
„ Chemical Elements in, . . 67 
„ Classes of, . . . .65 
„ Coma of, . . . .67 
„ Connection with Meteors, 69, 70, 71 
„ Constituent Parts of, . 66, 67 
„ Contraction of Head when 

near the Sun, . . . 66 
„ Elements required for calcu- 
lating Paths of, . . . 63 
„ Hyperbolic, .... 64 
„ Light of, . . . .67 
„ Origin of, . . . .71 
„ Parabolic, ... 65, 66 

„ Periodic, . . 64, 65, 66, 71 
„ Physical Characteristics of, . 68 
„ Tails or Trains of, . , 67 
„ „ Curvature, Density, &c., 68 

Compensation Pendulum, . . 103 

Constellations, Alterations in appear- 
ance, 
„ Probable Origin of the, 

„ Figures of the, . 

„ List of the, 

„ UsedintheStarCharts, 

Copernicus, ... 
Copernicus (Lunar Crater), 
Corona, the Solar, 
Coronids (Meteor System), 
Crab Nebula, . 
Crape Ring of Saturn, 
Cygnids (Meteor System), 



13 



17 

4 

2,4 

113 

118 

.93 

78 

, 38 

, 69 

29 

56, 57 

, 69 



PAGE 

D, Line in Solar Spectrum, . . 106 
D.M., contraction forDurchmusterung 

Star Catalogue of Argelander, . 114 

Day, Sidereal and Solar, ... 46 

Declination, Definition of^ . . 14 
Degree, Origin of, . . . 2, 14, 91 
Deimos, the outer Satellite of Mars, 50, 62 

Density, Definition of, . . . 35 
„ of the Planets, Sun, &c., see 
under the heading of each. 
Diameters of Lunar Craters and 

Walled Plains, . . 79 
„ of the Planets, Sun, Stars, 
&c., see under the head- 
ing of each. 
Diffraction Grating, . . . .106 

Dione, fourth Satellite of Saturn, . 62 
Distances of Moon, Planets, Sun, &c., 

see under the heading of each. 

Diurnal Rotation of the Earth, . 11 

Doerfel 63 

DoUond, 96 

Donati's Comet, .... 68 

Double Stars, 24 

Draconids (Meteor System), . . 69 

Dumb-bell Nebula, .... 29 

Durchmusterung Star Catalogue, . 114 



Earth, 

„ Apparent Angular Velocity of, 
„ Eccentricity of Orbitfor 200,000 

years, 

„ Form of, 

„ Length of a Degree of Latitude 

at various Distances from the 

Equator, . . . . 

„ Motions of, ... . 

„ Principal Facts about, 

„ Rotation Period of, . 

„ Velocity in Orbit, . 

Eccentricity, Definition of, 

„ of the Earth's Orbit, 

Eclipses, 

„ Number in a Saros 

„ „ „ X ear, 

„ Recurrence of Saros, . 

„ Relative Frequency of Solar 

and Lunar, 
„ Seasons, 

„ Year, .... 
Eclipses, Lunar, 

„ „ Apparent Diameter of 

Eiulh's Shadow in, 
„ „ Duration of, 

„ „ Number in a Year, . 

., Recurrence of the Saros, 
173 



45 
73 

46 
45 



, 45 
11 

61, 62 
11 

15, 45 

45, 46 
46 
82 

85, 86 
86 
85 

85 
85 
85 
86 

87 
87 
86 
85 



174 



INDEX. 



Eclipses, Lunar, till 1900 a.d.. Table of, 84 

Eclipses, Solar, 88 

„ „ Annular, ... 88 

„ „ Duration of, . . . 89 
„ „ Diameter of Shadow- 
Cone, ... 88 
„ „ Distance of Vertex Lunar 

Shadow from the 
Earth, ... 89 
„ „ Partial and Total, . 89 

„ „ till 1900 A.D., Table of, 83 

„ „ Velocity of Moon's Sha- 

dow in, . . . 89 
Ecliptic, The, defined, ... 14 
„ Limits, Lunar, 87 ; Solar, . 88 
„ Observed Obliquity of, for 

3000 years, ... 47 
Elements, Chemical, recognised in the 
Sun, &c., see under separate heading 
of each. 
Elements of a Comet's Orbit, . . 63 
Enceladus, the second Satellite of 

Saturn, 62 

Encke's Comet, .... 66 

Enoptron of Eudoxos, ... 3 
" Envelopes " in the Head of a Comet, 

66,67 
Equation of Time, . . . .121 
Equator, the Celestial, 11, 14, 91, 92, 103 
Equatorial Acceleration of the Sun's 

Motion, '36 

Equatorial Telescopes, . . . 103 
„ Mounting, . . . 104 

„ Adjustment for small 

Telescope, . . .110 
Equinoctial, see Equator. 
Equinoxes, Dates of the, ... 13 
,, Precession of, . . 2, 13 
Eratosthenes, his Meridian Instru- 
ment, 91 

Eruptive Prominences, ... 37 
Escapement of Clock, . . . 103 
Eudoxos, Sphere of, . . . 2, 112 
Europa, the second Satellite of Jupiter, 62 
Eye-pieces, Telescopic, . . .110 

Faculae 37 

Families of Small Comets, . . 71 
Finder for Telescopes, . . .110 

Flamsteed, 114 

Force, Eepulsive, Action on Comets, 68 

Foucault, 99 

Fraunhofer, .... 96, 105 
Fraunhofer's Lines, .... 106 

Galaxy, The, or Milky Way, . . 30 

Galileo, 94, 102 

Ganymede, the third Satellite of 
Jupiter, . . . . 54, 62 

Gascoigne, 100 

Geminids (Meteor System), . . 69 





PAGE 


Geocentric Latitude and Longitude, 


14 


Gnomon, The, . . . 


90 


Godfrey, 


108 


Graduation Errors of a Circle, . 


. 102 


Graham, 


103 


Granules, 


37 


Grating, Diffraction, 


. 106 


Gravity, Force of, . 


35 


„ „ „ on the Planets, 


. 62 


Great Nebula in Orion, . 


29 


Gregorian Telescope, 


97 


Gregory, 


. 97 


Groups of Stars, 


28 


Hadley, 98, 108 


Halley, 


17,64 


Halley's Comet, 


64,68 


Harmonic Law, 


58 


Heat received by the Planets from 


L 


the Sun, .... 


61 


Heliocentric Longitude, . 


116 


Hemisphere of Berosus, . 


91 


Henderson and the Parallax of a 




Centauri, .... 


19 


Herschel, Sir W., . . .31, 


58,98 


Hesperus, the Evening Star, 


43 


Hevelius, 


63,76 


Hilda (Minor Planet), 


51 


Hipparchus, . . 13, 91, 92, 112, 114 


Hooke, . . . . 16, 100, 108 



Huygens, .... 95, 100, 102 
Hydrogen, in the Solar Chromo- 
sphere, . . .37 
„ in the Stars, ... 22 
Hyperion, the Seventh Satellite of 
Saturn, 62 

Intra-Mercurlal Planets, ... 40 
Instruments of the Ancients, . . 90 
lo, the first Satellite of Jupiter, . 62 

Iron Meteors, 70 

„ in the Sun, . . . .106 

Japetus, the outermost Satellite of 

Saturn, 62 

Juno (Minor Planet), ... 51 

Jupiter, the Planet, .... 53 

„ Principal Facts about, 61, 62 

„ Satellites of, . . 54, 62 



Kepler, 



33, 63, 94, 95, 105 



Lacertids (Meteor System), 68, 69 

Lalande's Star Catalogue, . .114 
Latitude, Astronomical, ... 14 
Length of day at various latitudes 
(see Chart of the World, plate 20). 
Leonids (Meteor System), . . 68, 69 
Leverrier, . . . . .59 
Librations of the Moon, ... 76 
Lick Refractor, 97 



PAGE 

Light-year, the unitof stellar distance, 20 
Light, received by planets from the 

Sun, 61 

„ Time taken to reach the Earth 



from the Stars, . 
„ Velocity of, . 
Limb of the Sun, darkening of, 
Local and Standard Time, 
Longitude, Celestial, definition of, 

„ Terrestrial, 

Lucifer, the Morning Star, 
Lunar Eclipses, 

„ Ecliptic Limits, 
Lunation, 



20,21 
15 
37 
117 
14 
117 
43 

86,87 
87 
72 



61, 



Magnifying Power of Telescopes, . 109 
Magnitudes of Stars, . . 114, 115 

Magnitude of smallest Star visible 

in a given Telescope, ... 30 
Malvasia, Marquis of, . . 
Mars, the Planet, 

„ Principal Facts about, , 

„ Satellites of, . 
Mass of the Earth, . 

„ of the Moon, . . . 

„ of the Planets, . 

„ of the Sun, 

„ of various Stars, 
Mean Solar Time, . 
Medusa (Minor Planet), . 
Mercury, the Planet, 

„ Principal Facts about, 
„ Transits of. 
Meridian Circle, The 

„ Instrument of Eratosthenes, 

Mersenne, .... 

Meteors and Shooting Stars, 
„ and Meteor Streams, . 
„ and Comets, their connec- 
tion, .... 
Meteor Showers, ... 

„ Systems, Table of, 
Meteorites, .... 

„ Chemical Elements found 
Metonic Cycle, 

Micrometer, .... 
Milky Way, or Galaxy, . 
Mimas, The innermost Satellite of 

Saturn, .... 

Minor Planets or Asteroids, 
Mira, The Variable Star, 
Month, its Origin, . 

„ Different Kinds of, 
Moon, The, . ... 

„ Absence of Water in, 

„ Apparent Angular Velocity of, 

„ Craters on the, 

,, „ Dimensions, &c., 

„ Density of the, 

„ Eclipses of the, 

„ Ecliptic Limits of the, . 



100 
48 
62 
62 
45 
75 
62 
35 
22 

117 

51 

41 

61,62 

42 

102 
91 
97 

,70 
68 

70,71 
70 
69 
70 

,71 
85 

100 
30 

62 
51,52 
26 
2 
73 
72 
81 
73 
77 
79 
75 
86 
87 



INDEX. 



17J 



Moon, Elements and Principal Facts 

about, . . , . 62, 80 
„ Librations of, . . . .76 
„ Mountainsof, and their height, 77 
„ Orbit of the, .... 74 
„ Phases of the, ... 72 

„ Rotation of the, ... 75 
,, Sea-beds of the, ... 76 
„ Size of the, .... 75 
„ Surface, character of the, 76, 77 
„ Telescopic appearance of the, 76 
„ Walled Plains on, ... 78 
Motion of Stars in the line of sight, 

17, 18, 107 
„ of the Sun in space, . . 23 
Motions, Proper, of the Stars, . 17, 18 

Mountains, Lunar, their height, . 17 
Movement in Orbit of the Planets, . 67 
Mural Circle, The, . . . .102 
Muscids (Meteor System), . . 69 

Names of the Constellations, . .113 
„ of the Satellites of the Planets, 62 
„ of the Stars {see Star Cata- 
logue, p. 127). 
Nebula, The Spiral, . ... 29 

Nebulae, 29 

„ Annular, .... 29 
„ Distribution of, . . 29, 30 
„ Planetary, .... 29 
„ Spectra of, . . . .107 
Negative Eye- piece for the Telescope, 110 
„ Star-magnitudes, . .115 
Neptune, The Planet, ... 59 
„ Principal Facts about, 61, 62 
„ Satellite of, . . 59, 62 

New Stars, 28 

Newton, Sir Isaac, 13, 63, 96, 97, 105, 108 
Newtonian Telescope, The, . 97, 98 
Nodes of the Lunar Orbit, . . 74 
Nodical Month, The, ... 73 
Nucleus of a Comet, .... 66 
Nutation of the Earth's Axis, . . 15 

Oberon,Tlie Outer Satellite of Uranus, 62 
Object Glass, The Chromatic, . . 95 
„ The Achromatic, . . 96 
Oblateness or Ellipticity of the Earth, 45 
Obliquity of the Ecliptic, ... 47 
Occultation of Stars, Circle of Per- 
petual, 11, 12 

Olbers, 51 

Orbit of the Earth, ... 46, 61 

Orbits of Binary Stars, . . 24, 25 

„ of Comets, ... 64, 66 

„ of Planets, .... 61 

Orionids (Meteor System), . . 60 

P., Contraction for Piazzi's Star Cata- 
logue 114 

Pallas (Minor Planet), . . .51 



PACE 

Parallactic Rules, The, ... 92 
Parallax of the Moon, ... 74 
„ of the Stars, . , 20, 21 
„ of the Sun, .... 33 
Paths, Apparent, of the Stars, . . 11 
Pegasids (Meteor System), . . 69 
Pendulums for Astronomical Clocks, 103 
Penumbra of the Earth's shadow in 

Eclipses, . . 87 
„ „ Moon's shadow, . 89 

Penumbral lines, .... 89 
Perigee and Apogee of the Lunar 

Orbit, 74 

Perihelia of Comets, Distribution of, 71 
Perihelion of the Earth's Orbit, . 45 
Perseids (Meteor System), . . 69 
Phainomena of Eudoxos, ... 3 
Phases of Mercury, .... 41 
„ of Venus, .... 94 
„ of the Moon, .... 72 
Phobos, the inner Satellite of Mars, 50, 62 
Phosphorus, The Morning Star, . 43 
Photosphere of the Sun, ... 37 

Piazzi, 51, 114 

Planetary Data, Table of, . . . 61-62 
Planetary Nebulae, .... 29 
Planetary System, .... 39 
Planetoids {see Asteroids),. 51, 52, 61, 62 
Planets, Comparative Sizes of, . . 39 
„ Elements, and Principal 

Facts about the, . 61, 62 

„ Intra-Mercurial, ... 40 

„ Symbols of the, . . .61 

„ Trans-Neptunian, . . 60 

Plato (Lunar Crater), ... 78 

Pleiades, Star Cluster, ... 28 

Pole of the Earth, . . .11, 12, 13 

„ „ its place affected 

by Precession, . 13 
Pole of the Ecliptic, .... 13 
Pole Star, Ancient, Present, and Future, 13 
Positive Eye-pieces for Telescopes, . 110 
Praesepe, Star Cluster, ... 28 
Precession of the Equinoxes, . . 12 
„ „ „ Cause of, 13 

„ „ „ when dis- 

covered, 13 
Prime Vertical Transit Instrument, 107 
Prominences or Protuberances of the 

Sun, .37 

Proper Motions of the Stars, . . 17 
Ptolemy 33, 92, 112, 114 

QuadrantidB (Meteor System), . . 69 
Queen of Nebulas (in Andromeda), . 29 

Radiant Point in Meteoric Showers, 68 
„ Points of Meteor Systems, 

Table of, . . . .69 
Reflecting Telescope, various forms, 97 
Refracting „ Simple, . . 95 



PAGE 

Refracting Telescope, Achromatic, . 90 
Repulsive Force acting on ComeU?, . 68 
Retarding Medium acting on Cometp, 66 
Retrograde Movement of Satellites 

ofUranus& Neptune, 58,59 

)) „ of some Comets, 64, 65 

Reversal of the Spectrum, . . 106 

Rhea, the fifth Satellite of Saturn, . G2 

" Rice Grains," 37 

Right Ascension Defined, ... 14 
)) » determined by the 

Transit Instrument, 102 

Rings of Saturn, . . . .06, 57 

Roemer, .... 54, 100, 107 

Rosse, Lord, his Great Telescope, . 99 

Rotation of the Earth, ... 46 

„ of the Moon, ... 75 

„ of the Planets, ... 62 

„ of the Sun, ... 36 



93 
90 
62 
55 

56 
56 
57 
61,62 
56,62 
. 77 
. 63 
. Ill 
. 108 
86,88 

87 



Samarcand Observatory, . 
Saros, The, 85 ; Discovery of. 
Satellites of the Planets, . 
Saturn, The Planet, 

„ Cassini's Division in the 

Ring of, . 
„ Crape Ring of, 
„ Dimensions of the Rings of, 
„ Principal Facts about, 
„ Satellites of. 
Seas (Old) in the Moon, . 
Seneca, .... 
Separating Power of Telescope: 
Sextant, .... 
Shadow Cones in Eclipses, 
Shadow of the Earth in 
Eclipses, 
„ of the Moon in Solar 

Eclipses, 89 
» » » » Velocity of, 

on the Earth, 
Shepherd's Star, The, 
Shooting Stars, 

„ „ Materials of, 

„ „ Showers of. 

Short 

Showers, Meteoric, . 
Sidereal Day, . . . 
„ Month, 

„ Time, . . .10 

„ Year, .... 
Siderites and Siderolites, . 
Signs of Zodiac, 

„ „ „ No. of Degrees in a 
Siritis, Size, Spectrum, &c., 
Solar Apparent Time, 

„ Eclipses 

„ Ecliptic Limits, 
„ Solstices, 
Spectra of Comets, . 
„ Nebuliv, . 



89 
43 
68 
71 
70 
98 
70 
46 
73 
1-2G 
46 
70 
14 
14 
'22 
117 
83 
83 
91 
67 
id, 107 



176 



INDEX. 



107 
105 
107 

96 
109 

18 

14 



PAGE 

Spectra of Stars, . . 21, 22, 107 

Sun, . . . 105, 106 

Spectroscope, how used in astrono- 
mical research, 

18, 24, 28, 29, 37, 107 
„ how the Velocity of a 

Star is determined 
by it, 
„ Principles of, . 

Sphere, the Celestial, 
Spherical Aberration of a Lens, 
„ „ Tests for. 

Stars, Actual Velocity of, in Space, 
„ Ancient and Modern Position 

of the brighter, . 
„ Binary, , . . . 24, 25 

„ Catalogues of, . . 112, 114 

„ Charts of, ... . 115 
„ Chemical Elements recognised 

in, 22 

„ Classes of, . . . 22, 23 

„ Clusters of, . . . .28 

„ „ „ Distribution of, 

„ Designation of Individual, 

„ Distance of, 

„ „ „ how determined, . 

„ Double, 

„ Magnitudes, Methods of desig- 
nating, 
„ „ Negative, . 

„ Multiple, .... 

„ Motions of the, Apparent and 

Actual, . . . 11 to 18 

„ Nature of the, ... 21 

„ Numbers of, in each Magni- 
tude, .... 29, 115 
„ Positions, how affected by Pre- 
cession, . . .12, 13, 14 
„ Shooting, . , . . 68 
„ Spectra of, . . 22, 23, 107 
„ Temporary, 
„ Time taken by their Light to 

reach the Earth, . 
„ Triple, . . . , 
„ Variable, 

„ Visible to the naked eye, 
„ „ with different sizes o 

Telescopes, 
„ „ and invisible at differ 

entlatitudesand time 
of the year, 
Stereographic Projection, . 
Sun, The, ... 

„ Atmosphere, 
„ Chemical Elements in Atmo 

sphere of, ... . 106 
„ Chromosphere, ... 37 

„ Comparative Brilliancy of, . 36 

„ Corona, 38 

„ Cyclones in, .... 37 
„ Darkening of Limb, ... 37 



29, 30 
. 114 
19,21 
. 20 
. 24 

115 
115 

■24 



12 

117 

33 

37,66 



PAGE 

Sun, Density of the, . . 35, 38 

„ Direction of Motion in Space, . 23 

„ Distance according to Ancients, 

„ „ „ to modern 

determin- 
ations, 

„ Eclipses of, Annular, . . 88 

„ „ „ Total and Partial, 

85, 86, 88 

„ Equatorial Acceleration of Rota- 
tion, .... 

„ Facts about, 

,, Faculae, .... 

„ Granules, .... 

„ Heat and Light, how maintained 

„ Interior of the, . 

„ Light, .... 

„ Parallax of, how determined, 

„ Photosphere of the, . 

„ Prominences or Protuberances, 

„ " Rice Grains," 

„ Rise and Sunset, Table for find 
ing the Time of, 

„ Rotation of the, 

„ Size, .... 

„ Spectrum Classification of, 

„ Spots, .... 

„ „ Location of, 

„ „ Periodicity of, 

„ Temperature of, 

„ Umbra of the Spots on the, 

„ Velocity of, through Space, 
Synodical Revolution of the Moon, 
Syzygy, or Times of New and Full 

Moon, 



33 



34 



36 
38 
37 
37 
36 
37 
35, 36 
33 
37 
37 
37 

120 
36 
35 
23 
36 
36 
23, 36 
36 
37 
22 
73 

72 



Tables in the body of the volume {see 

list on page xi.) 
Tails, or Trails of Comets, 
Taurids (Meteor System), 
Telescope, Achromatic, The, 
„ Chromatic, The, 
„ Defects in the, 
„ EcLuatorial adjustment lor 

small, . 
„ Equatorial mounting for, 
„ Eye-pieces for the, . 
„ Finders for the, 
„ Instructions for using a 

small, . 
„ Invention of Reflecting, 

„ Invention of Refracting, 

„ Largest Reflecting, . 
„ „ Refracting, . 

„ Magnifying power of, To 

find the, . ' . 

„ Reflecting, Modern, or sil- 

ver-on-glass. 

Old, . . 

„ Refracting, Modern, with 

double object glass. 



67 
69 
96 
95 
109 

110 
104 
110 
110 

109 
97 
94 
99 
96 

109 

99 
97 

96 



Telescope, Refracting, Old, with sin- 
gle object glass, . . 95 
„ Stands for a small, . .110 
„ Tests for a small, . . 109 
Temporary Stars, . . . 26, 27, 28 
Tethys, The third Satellite of Saturn, 62 

Thales, 3 

Time, Apparent, Civil, Sidereal, 

46, 47, 117 
Timocharis, . . . . .91 
Titan, the sixth and largest Satellite 

of Saturn, 62 

Titania, the third Satellite of Uranus, 62 
Trains of Meteors, ... 68, 70 
Transit Circle, The, . . . .102 
Transit Instrument, The, . . . 100 
Transits of the inner planets, . 40, 42, 44 
Trans-Neptunian Planet, ... 60 
Triple and Multiple Stars, . . 24 
Twilight, Duration of, in different 

latitudes, .... 
Tycho (Lunar Crater), 



Tycho Brah^, 



121 
78 
63, 93, 100, 112 



Ulugh Begh, .... 
Umbra or Earth's shadow, 

„ or Moon's shadow, 

„ of Sun-spots, 
Umbriel, the second Satellite of Ura 

nus, ..... 
Unit of Stellar Distance, the Light 

Year, 

Uraniberg, .... 
Uranus, The Planet, 

„ Principal Facts about, . 

„ Satellites of, 



93 
87 
89 
37 

62 

20,21 
. 94 
. 58 
61,62 
58,62 



Variable Stars, Classes of, and Table, 

25, 26, 27 
Venus, Phases of, 

„ Principal Facts about, 

„ The Planet, . 

„ Transits of, . 
Vesper, The Evening Star, 
Vesta, The Minor Planet, 
Via Lactea, or Milky Way, 
Vulcan, The Supposed Planet, 

Walled Plains (Lunar), 
Water Clocks, . 
Wollaston, 

Year of the Ancients, 
„ Difl'erent Kinds of, . 

Zenith, or Point overhead, 
„ Telescope, 

Zodiac, how and when invented, 2, 4, 5 
„ Signsofthe,andtheirSymbols, 14 
„ „ Number of Degrees in the, 14 

Zodiacal Light, .... 38 





94 


61, 62 


43, 44 


. 44 




43 




51 




30 




40 


78, 79 


. 93 


. 105, 106 


. 2, 91 


. 46 


4,11 




108 



PRINTED BT GALL AND 1NGLI8, EDINBUEGH. 



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LIBRARY OF 



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